When having a tough time, I remember just what a "vow" means. A vow means maintaining your committment both when it is easy, AND when it is hard. When you want to, and when you don't. In sickness and in health.
A vow to myself, I remind myself, works the same way. Anybody can do it when it is EASY. Real commitment is staying true to your commitment even though everything in you is SCREAMING not to, EQ.
I'd tell myself: that is what makes sobriety valuable, because you must value it, and must treat it like a highly prized possesion that must be protected and guarded, always.