The purification process of yoga and meditation practice is like cleaning a drainage system that hasn't been cleared for a long time. Blocked drains can cause problems to our lives and the environment.
For some people the cleansing process is not necessarily pleasant.
Before we open the cover to look what is inside the drain we don't see any disgusting rubbish and it doesn't smell too bad. But as soon as we open the cover and look inside there might be bad smells or unsightly rubbish and waste floating on top. It can be quite unpleasant or disturbing. When we use a rake or net to remove the rubbish floating on the surface the smell becomes more intense and more undesirable waste is revealed. It becomes even more unpleasant or disturbing. If we generate aversion towards this experience, we might want to stop cleaning and replace the cover. We might not want to deal with the drain or the rubbish right now. And the drain continues to accumulate more and more rubbish and generates further problems in lives and in the environment.
It's similar when we practice yoga and meditation. It is an intense cleansing process. The mind needs to be cleansed regularly so that it doesn't cause problems to ourselves and to society.
The purification process can be unpleasant, or even quite painful for certain people. All the past accumulated mental and emotional tension that we have suppressed, or tried to run away from, comes up to the surface of the mind.
Some people retreat from the purification process, as they can’t bear or handle unpleasant experiences, while others are determined to go through the purification process without judgment or expectation, without craving or aversion, developing non-attachment and non-identification towards the mind and its contents, as they have developed a certain degree of understanding of the mind, and are determined to free the mind from impurities to benefit oneself and others.