I used to knit really tight as well, but I've gotten better
The thing that really worked for me is what has already been suggested here - I stopped giving the yarn an extra tug after a stitch. I was so used to doing it unconsciously it felt weird NOT to tug the yarn, now I can't imagine the time when it felt right to tug the yarn. It comes with practice
Just think of it as an excuse to keep on knitting!