In plain words
When we nurture all of these as desires, it turns into a great deception. All the desires we nurture are only roads to deception! Some day separation from them must come; there is no escaping it. Union has come about only for the sake of separation! They said that life is ‘an ocean of the clash of union and separation, with mighty towering waves’. Recognising this truth, we must gradually develop a feeling of indifference. Along with it, we must settle into a sukhāsana. We must recognise in which way of sitting we can follow this dhyāna in a manner that suits us. For this they said sukhāsana; they did not say padmāsana. Sitting in this padmāsana, as it is called, while the legs ache badly and this joint is very painful, it is not possible in the least for Manas to dwell on God. The āsanas done with this body, which is like a bubble of water, have nothing to do with the principle of the Ātma, eternal and real. In whatever way of sitting you find contentment in mind and body, you may choose that āsana. But you must keep in Manas, as the chief aim, the giving up of sense objects. This is the true āsana.
Prāṇāyāma is to regulate to some extent the vital breath that moves everywhere in our body
Now, the fourth is prāṇāyāma. For each to do this as he fancies is very dangerous. What moves everywhere in our body is air. This itself they call ‘prāṇa’. To regulate this prāṇa, which moves about at will, they call ‘prāṇāyāma’. That is, to check the air that moves about freely they call āyāma. Making āyāma of the prāṇa they called prāṇāyāma. Its inner meaning lies within this very word. In this prāṇāyāma we must observe closely the processes called pūraka, recaka and kumbhaka.