Asceticism is a lifestyle characterized by abstinence from sensual pleasures, often for the purpose of pursuing spiritual goals.  Ascetics may withdraw from the world for their practices or continue to be part of their society, but typically adopt a frugal lifestyle, characterized by the renunciation of material possessions physical pleasures, and also spend time fasting while concentrating on the practice of religion or reflection upon spiritual matters.  Various individuals have also attempted an ascetic lifestyle to free themselves from addictions, some of them particular to modern life, such as alcohol, tobacco, drugs, entertainment, sex, food, etc.

Asceticism has been historically observed in many religious traditions, (Christianity, Judaism, Islam, Buddhism), and contemporary practices continue amongst some religious followers.  Monks and nuns generally take a vow of poverty and renounce material, sensual pursuits.

The practitioners of this philosophy abandon sensual pleasures and lead an abstinent lifestyle, in the pursuit of spiritual elevation and enlightenment.   Many ascetics believe the action of purifying the body helps to purify the soul, and thus obtain a greater connection with the Divine or find inner peace. This may take the form of rituals, the renunciation of pleasure, or self-mortification. However, ascetics maintain that self-imposed constraints bring them greater freedom in various areas of their lives, such as increased clarity of thought and the ability to resist potentially destructive temptations. Asceticism is seen in the ancient theologies as a journey towards spiritual transformation, where the simple is sufficient, the bliss is within, the frugal becomes plenty.

                        --generally taken from Wikipedia

 

Henry David Thoreau led an ascetic life.  Not so much Edward Abbey, who indulged in earthly pleasures.