Mental blockage in the teachings of Yoga and Buddhism, is about when the mind is unwittingly being conditioned to think in certain way, to believe in certain belief, to analyze and judge everything under the influence of that particular way of thinking and belief, which influencing the mind to behave/act/react in certain way under the influence of ignorance, limited understanding/incorrect understanding, survival instinct, egoism and impurities.
And hence, the importance of mind purification process to free the mind from mental blockage even before being initiated into the different types of yoga practice for the thinking mind to silent itself, or to transcend its selfless function of the mind perception of a worldly life existence of names and forms, where both the perceiver and the perceived are subject to impermanence and selflessness.
Many yoga enthusiasts would think that the practice of renunciation and dispassion is the advance yoga practice that comes much later on the path of yoga, where it's only applicable to those who have been practicing yoga for a long time and who have already been through intense mind purification process.
Actually, renunciation and dispassion is indeed the basic practice that allows the mind purification process to be happening efficiently, by retreating and moving the mind away from such conditional worldly egoistic thinking and belief, to allow the mind to see the truth of things as it is, to free the mind from the habitual behavior pattern of egoistic thinking/judging/acting/reacting in certain way under the influence of ignorance, egoism and impurities.
The minds that are already free from ignorance, egoism and impurities don't even need to practice renunciation or dispassion, or any form of yoga practice.
It is because out of ignorance, egoism and impurities, most minds encounter great difficulty to free themselves from ignorance, egoism and impurities, as the mind only knows what it knows and what it knows are not necessarily the truth of what things are, and it's being conditioned by that limited impure and partial knowledge to be functioning and analyzing everything, and so, the important practice of renunciation and dispassion exists for helping the mind to be free from ignorance, egoism and impurities, practically and efficiently.
The minds are being told by this and that about what is good and bad, what is right and wrong, what is positive and negative, what is appropriate and inappropriate, what is happiness and unhappiness, what is deserving and non-deserving, what is meaningful and meaningless, what is joyful and painful sorrow, and so on. As long as the mind doesn't know how to be free from being conditioned by all those information/knowledge to analyze and judge everything, the mind will never be free even after spending the entire life span trying to practice yoga and meditation regularly looking forward to attain Samadhi, or to transcend suffering, as the modification of the mind is forever restless under the influence of ignorance, limited understanding/incorrect understanding, survival instinct, egoism and impurities.
In this present moment, the mind is free when the mind is free from being conditioned by any particular worldly egoistic impure thinking and belief, to think, analyze, judge and expect in certain way. The mind is not free it's because the presence of ignorance, egoism and impurities influencing the intellect of the mind to analyze and judge everything. Sincere renunciation and dispassion towards worldly affair, identity, connection, interaction and activity can practically help the mind to realize that freedom, that can purify the intellect efficiently and effortlessly, and not struggling by trying to analyze and reason everything under impure intellect influenced by ignorance, egoism and impurities.
Without renunciation and dispassion, the mind that wants to be free from suffering is like swimming in the ocean of sticky oil, while struggling to be free from sticky oil. The mind that is always swimming in the ocean of sticky oil is most probably got use to the presence of sticky oil, and it would be like fish out of water, if it comes out of the ocean of sticky oil.
After a prolonged period of time being dispassionate towards worldly object and engagement by retreating the mind from worldly egoistic affair, identity, connection, interaction and activity, then naturally, standing as a third party, the mind will start to be able to see the ignorance, selfishness, possessiveness and hilariousness in all kinds of worldly affair, identity, connection, interaction and activity under the influence of worldly egoistic thinking, belief, values and practice, influenced by ignorance, survival instinct, egoism and impurities. It's like those who are not swimming in the ocean of sticky oil, who can clean themselves efficiently from sticky oil by getting out of the ocean of sticky oil, who are free from the inconvenience of sticky oil, and looking at those who are enjoying yet struggling swimming in the ocean of sticky oil.
Inquire the truth of everything.