It's great you have a sense of humour. Good for you commencing something else so quickly
This is the way to prevent that happening again....So, you are almost finished and have one stitch left on the needle, you cut the ball away and there is a little tail of yarn..you pass that through the stitch you have, or you had, on the knitting needle and tighten. That will not come undone. I usually pull the knitting needle up and make that last loop larger and then pass the tail through and tighten that way..or..if you are worried you can always thread the yarn on to a needle and pass it through the loop (between yarn and knitting needle) while it is still on the knitting needle. Once the loop is safely through you can pull the knitting needle away and tighten properly. Then weave ends in.