Abstainer (noun)

A person who chooses not to do something, especially not to consume alcohol or drugs.

Origin:

From the verb abstain, from latin abstinere "to hold back".

Examples:

1. He was an abstainer from alcohol.
2. The group of abstainers were campaigning for stricter liquor laws.
3. The abstainer made a conscious decision to avoid certain activities.
4. The abstainer had a strong willpower.
5. The abstainer's decision was respected and encouraged by the group.