I'm only up to page 3 reading the replies, but I can't read the other 12 right now. But I wanted to reply, because I think there is a lot of wisdom in this thread.
My wife and I have been quilting for a couple of years, and have finished a few. We have struggled with the "doing our best vs. it doesn't have to be perfect" question several times. We have certainly improved as we tried different techniques and patterns. I think thing that has sealed the answer for me is when we give a quilt. The recipient (or the parents) are just in awe that we can even make a quilt. They look at all the pieces - even if it's just a simple 9-patch - and start to get an idea of what went into the quilt. They don't notice all the small errors that jump out at us because we know where they are. If we had a major error like a block out of place or turned wrong, we would definitely take it out and replace it, but the small stuff just isn't worth it. Finished is better than perfect.
Another thing we try to remember is that if we have done our jobs, this quilt will be falling apart in a few years because it has been used, washed, dragged around, and LOVED so much. I would rather the recipients love an imperfect quilt to death and ask for another one than to admire a nearly perfect one and not use it at all.
Darren