juen,
One thing which is essential is to understand that the methods of yoga, like any method, are simply neutral in themselves. Depending on the quality of these hands, you can create medicine out of it, and you can also create poison out of it. Any tool by itself is simply neutral. That is why if you are practicing these methods without a certain mindfulness, rather than being a ladder to more consciousness - it only take you into an even deeper unconsciousness. So this is one thing which is essential to be understood - that the methods of the spiritual sciences carry no quality of their own, it is the quality of the mind which determines the outcome of ones practice. For example, there are yogis who have been involved in the yogic sciences, not as a method towards their enlightenment, but as a means to nourish their own ego by developing occult capabilities of the mind, or there have been yogic who have been practicing for almost their whole lives but have remained in a deep sleep, no inner transformation has happened. Rather than helping to cut through the causes of ones sufferings, they have only magnified their sufferings. This is why it is very important to realize that it is the state of consciousness which is flowing beneath your practice which is going to determine the outcome of your practice.
If certain emotions and mental states like anger and frustration are happening as a result of your practice, one possibility is that the practice is unleashing certain repressed contents of the unconscious. Rather than trying to escape from such states, learn how to remain a witness in the present moment, without clinging to whatever may be happening in your experience, neither liking nor disliking, without attraction or aversion. If you want yoga to become a process of inner transformation, then you should know that there is nothing in life which is not yoga, because any situation if you approach it consciously, with awareness, can be turned into a process of growth and expansion. That is the whole skillful means of yoga - to come to know yourself, through and through, from the very source of your existence to its expression as a mind and body. But that is usually not our approach - we want to move towards what we like and avoid what we dislike, gravitate towards the pleasant and escape from the unpleasant - not realizing that what is pleasant may not necessarily be helpful for your well being, and what is unpleasant can be a tremendous opportunity to move beyond your limitations. Certain unpleasant mental states, if you approach them with a certain mindfulness, then it is a tremendous opportunity to come to insight into the activity of your own mind. In order to understand the functioning of the mind, we must first learn to see things as they are, one must learn to watch the mind without judgement. And that is the very essence of meditation - to witness the activity of the mind from moment to moment, just like a bright mirror reflecting without prejudice. Do not try to avoid your anger or any particular mental state - but keep the thread of awareness moving from moment to moment like an eye which never sleeps. If you are truly interested in coming to know of a freedom which is immeasurable, you will have to transform your whole life into a process of meditation.
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