I think it was Jenny Doan who said, "Finished is better than perfect." At least that is where I think I heard it. Just enjoy the process. It's those little imperfections that get better with time.
As for reducing the size of the quilt, I often find that the "field" of the quilt is large enough and I leave off the borders. I find it's harder to size square quilts. Rectangular block based quilts are easier to add a row at the top and botton or leave off a column of blocks on the sides. It's all in what pattern you choose.