That's the spirit! Believe me, if there's a knitting mistake left for me to make I don't know what it is.
Two words when you go to join the tails: SAFETY PINS. You'l;l need several big ones.
Stretch the needles out and lay out the bits the way you kow they should be, then safety pin the edge and put a safety pin on the right side (by which I mean the outside of the garment)--and make sure you've finished each on the correct row and in the same direction, because that's one of my favorite screw-ups. Fold the whole business where it's pinned, flattening it out, and pin the other side while it's lying flat. If it tries to curl up on you and argue about the project, pin on something with some weight to it to pull it down until the weight of the wool itself starts to straighten things out.
I figure some yarn is naturally hostile. Use anything you have to in order to beat the project into submission, and don't be the least embarrassed or ashamed to do so!