Whether we are consciously aware of it or not, the majority of the time we tend to go through life relying upon our own power and ability to carry us through. We think about all the things that we have to do; the money we must earn to make our livelihood, the daily tasks we must accomplish, the people we have to put up with, etc. If you go through Genesis and read prior accounts in the life of Jacob, you can see that there have been many occasions where he has done the same. Even here, where he wrestles with this mysterious man all night through, demanding a blessing, it appears to be him relying on brute force to get what he is after.
We can see all throughout the life of Jacob that he is a man of God, but there are so often times when he lapses and begins to rely on his own strength or cunning to get him by. In a way, we can be encouraged by this- the Bible paints a realistic picture of God's people, we don't have to live up to super-humans; they have strengths and weaknesses just like we do. It is the same back then as it is now: God enables His people and is the source of their strength, yet when we feel strong, we tend to forget that we aren't getting by with our own power.
God gave Jacob a new weakness, and sometimes He does the same to us. It's difficult not to grow bitter as we face our difficulties and weaknesses, but we must pray God helps us cope and remember that He has put us in whatever circumstance in order to remind us that we are to rely on HIS power, not our own.