You must make a self-control roll any time the GM feels you show an unreasonable degree of caution. If you fail, you must go ahead as though you were able to handle the situation!
Make a self-control roll whenever you must keep silent about an uncomfortable truth (lying by omission). Roll at -5 if you actually have to tell a falsehood! If you fail, you blurt out the truth, or stumble so much that your lie is obvious.