Evolution is not a process of continuous progression, rather it is coming to a stage of life, then standing still and harmonizing that area before taking another step. There is no continuous progression; it is stop, go, stop, go, stop. This evolutionary process is very natural and spontaneous. In order to be educated, to get our degrees and diplomas, we have to go through kindergarten, primary and secondary school, college and eventually university, moving in sequence from one class to the next. In the same way, we have to go through different stages in spiritual life, in relation to our karma and our awareness of karma.
The most important point to remember is to keep ahamkara, the ego or 'I' identity, in check and free from the influence of the gunas. There are two aspects of ego. One is the 'I' identity and the other is the simple 'I'. This simple 'I' is the drashta, or seer. When there is identification with the object of cognition, that is ahamkara, the 'I' identity. For example, a beautiful flower can be seen in two ways. One way is to see the beauty and shape and to appreciate it. That is the simple 'I', an acceptance that the flower is there. The other way is to desire the flower, pick it, take it to our room and put it in a vase. That is ahamkara, where there is no appreciation of the flower in its natural form, but the desire to take it and keep it with us.
Keeping this aspect of desire in check has been mentioned in the fifth chapter of the Bhagavad Gita. We must begin to observe and appreciate the natural form, not only of the world, but also of ourselves. An effort has to be made to change the direction of the mind. In order to overcome that aspect of 'me' identifying with the objects and situations, we must re-educate the mind to appreciate, and not to want, desire or crave. This is a part of sadhana which has to be understood and realized in meditation.
Re-education of the mind can only be done through the stages of pratyahara, because in this state there is already dissipation and we try to focus and centre ourselves in that state of dissipation. So, this mental education is to be provided in pratyahara and not in the stages of dharana or dhyana. In dhyana, we are experiencing the continuity of consciousness. In dharana, we are experiencing the one-pointed, focused state of consciousness. In pratyahara, we are educating and re-educating the mind, the nature, the gunas and the vrittis, the tendencies of mind. Therefore, pratyahara is an important aspect of life.