Archar,
“Besides practicing to control breath in yoga should we do some exercise or follow some diet plan to get more energy level?”
There are many things that could be done, and which if a person is committed towards, can be achieved much sooner than one can expect - but it is all a question of whether one is willing to initiate the effort. This will require enormous willpower to see things beyond one’s likes and dislikes - because most of these techniques will require you to function in a way which is beyond your likes and dislikes. If you don’t like it - it doesn’t matter, you stick to the discipline. Like this - much expansion can happen in a very short time, but it will require your committed attention and energy. So that is the first thing to understand.
Every aspect of the way one is living life has an impact on the conditioning of the mind as well as the subtle energies which are flowing through one’s system. So, one will have to deal with everything. One can either change everything, or change nothing. As far as diet is concerned, the kinds of foods which help to bring about a transformation in one’s system are those which are of a “sattvic” kind. Every kind of food has a range of vibrations. The gross part is absorbed by the body, the subtle part is absorbed by the mind. Fruits, vegetables, nuts - these kinds of foods have that range of vibrations which help your mind come to a state where it can become purified more easily. It creates psychological tendencies which help you remain balanced, calm, relaxed, and clear. Although these are not garunteed - because whether a person is balanced or not really has very little to do with what they are eating. Adolf Hitler was a vegetarian, and he was amongst the most violent human beings who has been here. Controlling what you eat at the most will help create tendencies in the mind which will assist you in your expansion, but without your awareness, it is useless. Everything has to be done with awareness, because the basic root causes of man’s suffering are because he has been living for millenia out of unawareness. You can practice all these techniques, but if you are just doing it mechanically, out of unconsciousness, then they are not going to be of much help. If you are going to control what you eat and restrict your diet to a vegetarian diet - then you will have to do a bit of research and educate yourself as to what you need to have a balanced diet. This will differ from person to person.
Another thing which can help to transform the subtle energies of the mind and body is celibacy. This is not out of a condemnation for sex. It is simply a scientific way to gather more energy so that you can channel that energy into your practice. If you remain celibate and gather the sexual energy - you will find for example that it strengthens your concentration enormously, which helps when you start doing the work of meditation. It also assists in awakening of the Kundalini and purification of the chakras. But - one should be careful to take this celibacy to the extreme. Nature has not created man to be celibate - it is just a fact. And if you remain celibate for too long, what will happen is that your mind will simply become sexually repressed. One may think over time, because of conditioning, that one has become free from sex - but it is not really the case, all of one’s sexual desires have simply been repressed in the unconscious. So celibacy is useful according to my understanding, but only as a temporary method.
At what times during the day you practice will also have an influence. The body and mind are synchronized with certain cycles of nature. In twenty four hours- the body goes through certain bio-rhythms which are connected with the cycles of the sun and the moon. Because of this, at different times during the day, different energies will be active in your system. This can be observed with something as simple a the breath. At different times during the day, the breath will be found to be flowing more either through the left nostril, the right nostril, or at times equally through both nostrils. When the left nostril has become active, the right brain hemisphere becomes active, as well as the ida nadi in the subtle body. When the right nostril becomes active, the left brain hemisphere becomes active, as well as the pindala nadi in the subtle body. When both nostrils are equally active - the sushumna, the central channel along the spinal cord, has become active. During those times during the day when the sushumna is active, there is a greater likelihood of awakening Kundalini as well as deeper states of meditation. So one should practice during those times of the day when the sushumna is active. I will not mention them all for the sake of safety, but one time during the day when the sushumna is active is during sunrise, approximately between four and six a.m.
Another method of helping transform the subtle energies of the body involves piercing the body at certain places to awaken specific nadis, but I do not wish to speak too much about this method.
The use of specific herbs can also be of great assistance in purification of the nadis and strengthening the concentrative power of the mind (joriki). Some herbs which can be of assistance in developing concentration are gingseng, sage, gingko biloba, and peppermint. Green tea is also effective in purification of the nadis.
During the course of your sadhana in the beginning, practice with consistency kriyas (purification exercises). A good kriya to begin with is jal neti, and if you only practice jal neti everyday, that is enough to help purification of the nadis tremendously if it is combined with other disciplines such as pranayam and asana.
There are other methods which can help one’s expansion of consciousness tremendously, which are of a tantric nature, but I do not feel that they are suitable to be mentioned as they require somebody to have already gone through a certain amount of mental training.