Japa, imagery work and breathing exercises can be helpful to an extent if at the core of sadhana is a genuine seeking and a true aspiration. Done mechanically they can give us some experiences by force opening an inner door but the core aspects of spiritual life, its core truths cannot come by these means. They come by the Grace which watches over our efforts and sees not just the effort but most importantly the sincerity of our seeking. What is important is aspiration, faith, sincerity, surrender and the right attitude towards life and work and the yoga itself. The more our ego-centricity is diminished, the more we grow in faith, devotion and consecration, the more readily the Grace opens the doors. We may even say that it is because of the Grace that one can develop these fundamental elements for the yoga. However there are yogas that do not believe in Grace and give too much space to personal effort or their conception of divinity is more like an impersonal state that generally rely on mechanical methods. To each the Divine responds according to our faith and if we believe that He is not a Being but a state that can be acquired by mechanical means He seems to come to us in that guise.
Japa is no doubt a powerful means to open the doors of the higher consciousness. It has the additional impact upon the physical mind and also the body. Here one can use any Name or mantra which represents for oneself the Divine. There are of course some well-known sound symbols and mantras that have been used traditionally for millenniums and hence are charged automatically such as the word OM or the Gayatri Mantra. There are other mantras, especially the beej mantras that need a Master who has realised that particular mantra to charge it by his power of tapasya before the disciple can use it. It is however best if the mantra arises spontaneously in the heart in which case it means that the mantra is meant for the person. A mental choice of the mantra is the next best choice. In the Integral yoga generally it is enough to take the Mother’s Name or Sri Aurobindo’s. There are of course some mantras given by Sri Aurobindo to different sadhakas or written at different occasions. Some of these are in the traditional Sanskrit words, others are in English. Of course the whole of Savitri has been described as a mantra of transformation.
So too with images. Actually our mind is all the time forming images because of the faculty of imagination that we hardly train or use. In a certain sense the whole world as we experience it is an image conjured by the Mind upon That which escapes all percept and concept. These images then trap us by conditioning and habit. But here too we can use our imagination and the capacity for images in a powerful way as a lever to open a door. The principle behind it is this that whatever we imagine and visualise the Reality begins to assume that form and shape. It may take a long or short time but sooner or later IT begins to ‘appear’ as if it is what we image it to be. Hence its usefulness for our progress. At the same time a reliance upon this method alone can trap us in certain formulations of the Divine and close us in limited formations of what exceeds all forms and formulations. It is because of this that certain practice advice to meditate upon impersonal states such as Peace etc. rather than through concrete images such as flame. The former method leads to Nirvikalpa Samadhi whereas the latter to Savikalpa Samadhi. but Truth exceeds both and hence here again it is best to focus on aspiration and surrender and leave it to the Divine to reveal Himself the way He chooses to.
Breathing exercises are, in my view, at best a preparation. They can give us some experiences in the vital if done intensely or else they can calm the mind and well as energise it by regulating and balancing the flow of pranic energy into the human system. But their spiritual utility is very doubtful. They are also likely to increase our ego because of certain powers that accompany the experiences of the vital worlds. Equally these vital zones can trap the soul by creating an illusory world that imitates the spiritual.. This is especially so when the sadhana is motivated by ambition and seeking after powers.