Self-Regulation falls under the virtue category of Temperance. Temperance deals with strengths that protect us from excess. It is the practiced ability to monitor and manage one's emotions, motivation and behavior in the absence of outside help.
Self-Regulation can be viewed as a resource that can be depleted and fatigued. A useful metaphor can be that self-regulation acts like a muscle, which can be exhausted through over-exertion or strengthened through regular practice.