What the body can do and cannot do, is not important.
What the mind can achieve and cannot achieve, is not important.
Peace, compassion, and the ability to let go, is not determined by what the body can do and cannot do, or what the mind knows and doesn't know about the different names and forms, the characteristics and the purposes of the many things that exist in the world of names and forms, as well as what the mind achieves and doesn't achieve by utilizing the intelligence and accumulated knowledge.
Knowing and memorizing many names and forms, and their characteristics and purposes, doesn't change the truth of names and forms being selfless and impermanent regardless of all the different qualities, and it doesn't determine the ability of seeing things as they are without grasping, or the capability of non-attachment, non-identification, non-clinging, non-longing, non-craving, non-aversion, and letting go what the mind perceives, judges, thinks and believes as good and bad, right and wrong, positive and negative, pleasant and unpleasant, meaningful and meaningless, deserving and undeserving, and so on, according to certain worldly thinking and belief, values and expectation.
What the body can do and cannot do, or what the mind can achieve and cannot achieve, is impermanent. No matter what the body can do or cannot do, no matter what the mind achieves and doesn't achieve, this body and the modification of the mind, or the perceptive, cognitive, assertive thinking faculty of the physical body, is subject to selfless impermanent changes of decay, weakness, injury, illness, pain, old age, death or decomposition, being powered and influenced by energy and elements.
Above all, there's no 'I', or individual being existing, to be in control or altering the truth of selfless impermanent changes that is governed and influenced by the law of nature, or cause and effect. There's no 'I' existing to be going through impermanent changes of decay, weakness, injury, illness, pain, old age, death or decomposition, but merely the limited adjunct of the body with the perceptive cognitive assertive modification of the thinking emotional mind.
If being physically and mentally fit, strong and flexible determining a person as a 'yogi', then all the competitive athletes especially gymnasts and contortionists, who are also possessing the strong mental quality of concentration, focus, determination, perseverance, will power, forbearance, positive thinking, and etc, on top of the extraordinary physical ability to perform certain actions, as well as all the intelligent knowledgeable scholars and scientists, are all 'yogis'. But, it's not necessarily so.
The most healthy, strong, flexible, intelligent and knowledgeable human beings in the world might not be free from the perception of physical/mental/emotional suffering and have no peace, if the mind is not free from ignorance and egoism.
What distinguish 'the yogi' from the competitive athletes, gymnasts and contortionists, as well as the scholars and scientists, is the presence and absence of non-attachment, non-identification, non-craving, non-aversion, non-judgment, non-comparison, and non-expectation. More importantly, 'yogis' or not, all are subject to selfless impermanent changes, however, 'the yogis' are resting in unconditional peace, transcending the modification of the mind, of a selfless impermanent worldly life existence, not being disturbed or determined by the ceaseless and selfless impermanent changes in the body and the mind, and in everyone and everything in the world, not being disturbed or determined by the actions and fruit of actions. Meanwhile the others of the many different qualities, abilities and limitations, might be disturbed and determined by the selfless impermanent changes, being restlessly swaying in between satisfaction and dissatisfaction, happiness and unhappiness, meaningfulness and meaninglessness, enjoying or suffering, being influenced and determined by the actions and fruit of actions, success and failure, abilities and disabilities, pleasantness and unpleasantness, desirable and undesirable life experiences, likes and dislikes, agreements and disagreements, good and bad relationships with all and everything, the conditions and situations in the world, and so on, perceiving all kinds of suffering due to ignorance and egoism.
Competitive athletes, gymnasts and contortionists, intelligent scholars and scientists, as well as anyone who are not as physically or mentally fit and strong as them, also are 'yogis', if the mind is free from egoism of attachment, identification, craving, aversion, judgment, comparison and expectation.
Being mentally positive and optimistic, or being good, righteous, kind, loving, generous, happy, content, grateful, cheerful, forgiving, sympathetic and empathetic, also doesn't change the truth of selflessness and impermanence of this body and mind, and all kinds of names and forms that are existing in this world being perceived through the selfless thinking assertive intellectual emotional mind.
There's not even the idea, or identification of, "I am practicing yoga and I am a yoga practitioner", or "I am a yogi," not to say, "I am a good or bad yogi."
This teaching that distinguishes 'the yogis' from 'the non-yogis' is beyond worldly egoistic judgment and comparison, where it's not about comparing between the qualities of 'yogis' and 'non-yogis', to judge who is better/worst or who is superior/inferior. But, it's about whether one realized the truth of names and forms, being free from ignorance and egoism, and is peaceful as one is, or not, regardless of all kinds of different qualities. It's about looking at the different names and forms, and to reflect upon the one same truth of all kinds of names and forms that portray different qualities from one another. It's about knowing what is yoga, what is the yoga practice, what is the main purpose of practicing yoga, and how to realize yoga through the practice.
Regardless of good or bad quality, all are impermanent. If there's attachment towards either good or bad quality, not respecting the law of impermanence, there will be suffering arise in this mind. And there's nothing wrong if the mind doesn't want to be free from attachment. It's everyone's freedom for what they want and don't want. However, a disturbed mind in pain or anger might not have self-control to not generate actions that would hurt oneself and/or others, and the surrounding environment. That's all.
'The yogis' look at things, they see the selflessness and impermanence in all and everything, regardless of the different qualities, void of desire of craving and aversion towards the different qualities, respecting the law of nature, respecting all the impermanent changes as they are. There's no clinging or longing towards 'good' qualities. There's no aversion towards 'bad' qualities. They live and perform actions among the worldly minded, but the mind is void of disturbs, hurts, sorrow, fear and worry.
'The non-yogis' look at things, they see the different qualities, and generate likes and dislikes, agreements and disagreements, and the desire of craving and aversion towards the objects of names and forms that the mind perceived through the senses. From there, restlessness arise upon discontentment and unwittingly chasing after the names and forms that it desires, and trying to get rid of the names and forms that it doesn't desire, where suffering arise upon non-gratification of the desire of craving and aversion, when it gets what it doesn't desire and doesn't get what it desires, when things don't happen in the way that it desires and expects it to be. The mind misses the people, the objects, the relationship, the interaction, the goodness, the happiness, or the meaningfulness that it likes and desires, but are absence in the present moment. The mind reacts with and suffers from disturbance, disappointment, dissatisfaction, unhappiness, hurts, painful sorrow, grief, guilt, regret, anger, hatred, fear and worry, upon coming in contact with undesirable/disagreeable experiences, and upon not coming in contact with desirable/agreeable experiences.
There are some highly intelligent creative minds in the world of advanced technologies, as well as there are some wise and compassionate 'yogis' in the world of selflessness and impermanence, but can they stop the ignorance, egoism, suffering, hatred, discrimination, greed, jealousy, corruptions, wars, violence, illness, old age, death, and so on in the world of limited adjunct? Nope. Not even enlightened beings in the present or in the history can do anything to change or control the world to be or not to be in certain way. It's all about self-transformation. One can only liberate one's mind from ignorance and its by-products. This path is alone, but not lonely.
Inquire the truth of everything.