Asceticism is founded on the idea that you can get closer to spirit by detaching yourself from matter other than what is strictly necessary to maintain life in the physical body. It has a long history and appears in most religions in various forms ranging from fasting to celibacy and other physical privations up to and including deliberately inflicting pain on oneself. I once met a man in India who had remained standing for several years. He lived in the forest with a couple of disciples and neither sat nor lay down though he had a simple wooden bar to lean on. There is also the famous Jain statue at Sravana Belagola which depicts a naked man standing upright in deep meditation who has been in that position so long that vines have grown up around his legs. Obviously that is a fantasy but it depicts an attitude of great ascetic self-control, endured in the attempt to gain spiritual mastery. In India these austerities are called tapas which is a word with the root meaning of heat or fire and implies that such an activity burns away all the material dross in the aspirant's lower nature leaving just the shining spiritual core behind.
There may have been a place for such things at one time. In a world before a developed mental focus arose, complete mastery of the body might have been a major part of spiritual development. However, the antiquity of these practises indicates that that period was a long time ago. Even the Buddha renounced extreme asceticism, and it is notable that Jesus was not an ascetic and nor did he require his disciples to be such. That does not mean that there is no need to subdue the physical side of being. There most assuredly is but its place is not paramount. The body is part of the totality of what we are but it is a part that should be under the rulership of the higher parts, higher because they are more conscious, freer and closer to the essential nature of what we are.
God looked at the world and saw that it was good. This tells us that extreme asceticism is not good because it denies the virtue in creation. On the other hand, it is a fallen world and we must overcome the fallen part of our own nature in order to become properly responsive to spirit. The lower must be dominated so that the higher can make itself known to the fullest extent. This is the basis of asceticism but the ascetic should not deny or try to kill the lower. This is the mistake of the gnostic who sees matter as evil thus failing to realise that it is not matter which is evil but materialistic consciousness. To see matter as evil is to destroy creativity and love, and a spirituality without creativity and love is a desiccated sort of thing which may bestow a kind of psychic power, as tapas was traditionally thought to do, but will do so at the expense of a deeper, truer and richer spiritual understanding.
The balance between the ascetic and the physical has in the past not always been found. Apart from the severe self-mortifications of certain mystics there have been sects that have gone the other way and decided that since everything is holy we have been given the green light to do whatever we want which includes sexual over-indulgence. That is wishful thinking at best and downright stupid however you look at it. The body has its place but should always be seen in the light of the soul to which it must be sublimated. Everything may be holy but there is a hierarchy. To allow physical instincts to override spiritual focus in this way is the result of an unbalanced and corrupted imagination and will lead to spiritual disease. Matter may be the means through which creation is expressed but unless it is submissive and open to spirit, as was the Blessed Virgin Mary, it is not holy.
Even now there may be certain periods in a disciple's life when asceticism is required. However, such an approach is not generally demanded any more than long periods of meditation are necessary. These may even be harmful and assuredly will be if they lead to spiritual isolationism and pride. Nonetheless, if the material side of one's being should not be seen as an enemy to be totally beaten and crushed, it should still be tamed and brought under conscious control to the point where it is a more or less pure vessel for the soul. This, of course, is its natural state and has only become otherwise because of our disordered way of being. Asceticism is like a medicine needed to cure a sickness. A spiritually healthy person requires no such medicine and will automatically respond to the body in a spiritually healthy way with neither indulgence nor disdain.