As for relaxing, I used to be really tense, and even hold my breath sometimes without realizing it. It just takes time, and a good solid, seat and the confidence that you can ride well without thinking about it every single second. If you can try bareback, this practically forces you to relax and trust yourself and your horse. Sitting trot is also a good test for relaxation- if you're wondering if you're too tense, go into a sitting trot. Do you move with the horse, or do you bounce all over the place? If you're bouncing, that may be a sign you were too tense (or that you tensed going into
the trot...so it's not the MOST reliable thing ever
). Also try to have someone in the arena with you if you don't have an instructor and shout out to you if you're too tense. Even non-horse people can tell when someone on horseback is tense.