What make the yoga practice appears to be difficult or unpleasant?

The presence of certain physical and/or mental weakness, illness, injury, limitation, inability, and disability, doesn't make the yoga practice difficult or unpleasant.

Cannot, or don't know how to perform certain, or many, or all of the yoga poses, breathing exercises, concentration exercises, or some other forms of yoga practice, either being limited by certain limitation physically and/or mentally, it doesn't make the yoga practice difficult or unpleasant.

Cannot understand some, or many, or all of the teachings of yoga, due to the limitation of intellectual reasoning or language barrier, also doesn't make the yoga practice difficult or unpleasant.

It's the presence of intense mental blockage that make the yoga practice appears to be difficult, or unpleasant, or even wrongful and painful to the mind, especially in the beginning of the purification process, where more and more impurities are being exposed, or appearing to the surface of the mind. Such as -

Deep ignorance and egoism.

Intense impurities and restlessness.

Intense ego, or idea of 'I'.

Deep rooted pride and arrogance.

The over-powering sense of superiority or inferiority (intense high self-esteem or low self-esteem).

Closed minded.

Intense clinging, craving, or longing.

Obsession towards certain names and forms.

Intense superstitious.

Intense physical or mental addiction towards certain names and forms.

Intense attachment towards worldly knowledge, ideas, thinking, belief, values, and practice.

Intense passion.

Intense anger, hatred, bitterness, vengeance, and resentment.

Intense selfishness, possessiveness, separateness, prejudice, greed, and desire of craving and aversion.

Intense personal and group identification towards particular quality of names and forms.

Intense attachment towards the physical and mental condition, ability, and achievement.

Intense judgment, comparison, competition, and expectation towards oneself and/or others.

Unable and/or unwilling to let go the past and/or the future.

Unable to accept the reality as it is, or the selfless impermanent changes, as they are.

Reluctant to learn.

Reluctant to surrender or let go the urge to 'control' and/or to 'be in control' towards everything to be and not to be in certain way.

Reluctant to make adjustment, adaptation, and accommodation.

Reluctant to forbear or withstand even the slightest unpleasantness or difficulty.

Lack of patience, determination, and perseverance.

Lack of self-discipline and self-management.

Lack of minimal degrees of self-independence.

Expecting everyone and everything to be exactly the way that 'I' like it to be, or the way that 'I' think how it should be.

Intense resistance or aversion coming from the mind towards what it dislikes, unfamiliar with, uncomfortable with, and disagrees with.

Hypersensitivity.

Intense defensiveness and offensiveness.

Laziness (idleness).

Hyperactivity (restlessness).

Unable or unwilling to observe the middle path or to let go extremity.

Chasing after pleasurable enjoyment or indulgence of the senses.

Chasing after love, attention, agreement, liking, acknowledgement, recognition, acceptance, validation, sympathy, empathy, name, fame, admiration, glorification, status, respect, power, wealth, and etc.

Uncontrollable lust.

Blind-believing, blind-following, blind-agreeing/disagreeing, blind-practicing.

Chasing after perfection, fairy tales, rituals, miracles, super extraordinary power, and transcendental mystical experiences.

Being over-powered by the worldly practice of politicking, hypocrisy, and untruthfulness.

Boundless desires, ambitions, or aspirations.

And so on.