Thoughts of Mitzvos Save One From Aveiros:

The Sefas Emes (Parshas Haazinu, 5634) proves that good thoughts are very potent from a kal v'chomer. The Gemara (Yoma 29B) says that thoughts of sin are worse than actual sins. If so, since we know that “middah tova merubah" (the measure of good is bigger than the measure of bad), it is certain that when one thinks that he wants to do mitzvos, he has accomplished more than he could hve even from actually doing mitzvos. He adds that such thoughts also help a person avoid all sin.