You can't expect perfection from your first project (or one after that, for that matter). Your corners are going to be a little wonky. Your blocks are going to be a little lopsided. :) Your little girl won't care a bit. She's going to be thrilled to have it, and you're going to be more than proud to have finished your first one.
I don't have much piecework under my belt...so I'm right there with you. What I can tell you is that you'll gradually get better as you go along without realizing it. By the time you near the end of your 2nd or 3rd project, you'll catch yourself saying "that doesn't look half bad".
<hug> Hang in there and keep up the good work.