Don't be so hard on yourself. It does take some time and practice, but every time you do a project, you'll get a bit better.
As far as perfection - well, it's over rated. I'm not suggesting that you do shoddy work, whether it's for yourself, a swap or a gift. Look at the overall piece, rather than a point or two that is missing or floating when it shouldn't be.
If you really don't think your work is up to par at this point, explain that to the hostess, then use the blocks to make a charity quilt. If you can relax a bit so that you enjoy the process, some day you'll look back and be glad you didn't give up.