I strongly believe in sowing and reaping. Some people might believe in karma, some in 'what goes around, comes around.'
The basic principle here is that everything has consequences.
I just loved a recent episode of House because it was about sowing and reaping. Balance, even. The dad sacrificed everything to save his son, and being the wonderful show it is, the son lived. Not only that, but the minor characters have made some choices that are now beginning to bear fruit (and add conflict).
Are you making sure your characters are suffering from their bad choices? Being rewarded for their good ones? It's the little choices at the beginning of the story that should affect the rest of the book. I think these seemingly inconsequential choices should weave together and create the plot.
What do you think about sowing and reaping? Is your MC making good choices or bad ones, and how does that affect your character's moral arc?