Refrain, abstain, forbear are comparable when they mean to keep or withhold oneself voluntarily from something to which one is moved by desire or impulse.
Refrain is especially suitable when the checking of a momentary inclination is implied.
At times, to refrain from an action implies merely its nonperformance.
Abstain is more emphatic than refrain , because it usually stresses deliberate renunciation or self-denial on principle and often implies permanency of intent.
It is used especially in reference to those natural appetites and passions whose control or renunciation are a part of self-discipline.
Forbear usually implies self-restraint rather than self-denial, be it from patience, charity, or clemency, or from discretion, or from stoicism.
But often forbear is but vaguely distinguishable from refrain .