When shall we cross ourselves?

Whenever we are about to perform a good deed, or when we see or feel that we might commit a sin.

• Carlos Gimenez, Barrio (Context: children in a religious institution are answering catechism questions)

This sounds like a great way to prime yourself. Crossing yourself has all the wrong connotations, but a gesture meaning "I choose good." should help in general. (I like the fist-over-heart Battlestar Galactica salute.)

Having a whole set of gestures, along with pithy quotes, should prove even more effective.