Mortification of the flesh
In its simplest form, it can mean merely denying oneself certain bodily pleasures, such as by abstaining from chocolate, from meat, from alcohol, or from sex. It can also be practised by deliberately choosing a simple or even impoverished lifestyle; this is often one reason many monastics take vows of poverty.
In some of its more severe forms, it can mean actually inflicting pain and physical harm to oneself, such as by beating, whipping, or other means. Some psychologists associate this practice with algolagnia.
Mortification of the flesh is practised in various ways by members of several different religions, including Christianity (particularly Eastern Orthodox and Roman Catholic monks), and Islam (particularly in Sufism).
It has been speculated that the more extreme practices of mortification of the flesh may be used to obtain altered states of consciousness for the goal of experiencing religious experiences or visions.
See also: flagellation.