Abstention is when someone deliberately avoids doing something, especially something that might be harmful.
You might decide to live for a year without buying anything besides food — you could call the act of doing this abstention from the consumer lifestyle. Other kinds of abstention might include resisting junk food or quitting smoking. To abstain is to hold back or shun something. The root of both words is the Latin abstinere, "withhold, keep back, or keep off."