There is a classic question asked of Yakov Avinu. Why does the Torah tell us that he was struck with intense fear. After all, he had already received a promise from Hashem, that he would be protected in all that he did. Was Yakov doubting this Divine promise.
The classic answer to this question is that he was afraid שמא יגרום החטא, that perhaps he has sinned during his twenty years with Lavan, and perhaps that canceled out the blessing.
There is a precedent for such fear, as Rashi points out in Masechet Brachot, that the return of Ezra in rebuilding the Second Temple, did not have the same glory as in the days of Joshua, when he brought the Egyptian exiles into the land. Ezra was under Persian rule that was caused by the sins of the Jewish people.
The Maharsha makes an interesting clarification. There is such a concept that when one is saved miraculously, he uses up some of his merits. These are the merits that determine if one is worthy of the ultimate blessing when he leaves this world. Yakov had no problem giving up some of his merits to defeat Eisav.
The point of the Maharsha was that Yakov didn’t care about that. His only concern was whether he had acted improperly in the eyes of G-d, and this would cause a loss of his protection.
This is a good lesson for all of us. We should always be on guard to continue acting in a way that is pleasing to G-d. This will be our guarantee that we will always have protection from above.