My weakness is that I don't always get around to the final detials on a project. I used to leave about the last 10% undone, and after a lot of will power, I am down to about 1 to 2%. Still, that last little bit hangs there and bugs the heck out of me.
The problem is that I don't think those final little things will actually take any time, so I dont plan for them ... and I am usually planning my next project about half way through my current one. So my resolution is to push all the way through to the last detail.