The book ספר הישר, written by Rabbeinu Tam, the grandson of Rashi, has some unique insights into human nature. He is very much in tune with human failings and the difficulties that people need to overcome. An example given by ספר הישר refers to a person who is convinced of the truth of the Torah and he wants to begin observing Mitzvot diligently. He even learns about all of the pitfalls that could turn a person away from observance. He is now completely ready to start his spiritual, observant life. Rabbeinu Tam points out that his next major obstacle is to break his previous bad habits. Discipline and creating new good habits, is very hard to attain. So many people want to do the right thing but are so fixed in their ways that they are unable to make the changes they desire. The suggestion is to first get psyched up to make the transition and then resolve to discipline oneself. This can lead to success in one's spiritual mission.