Sometimes I get nervous before I ride too. What I have been doing is getting to the barn earlier so that I can spend more time with my horse, and I don't have to rush while getting ready. This calms me and my horse down and gets me in a good mood before I get on.
A few years ago I went through the same thing Sophia. Every time I got on my horse I would become terrified that I would fall of and become paraplegic or something terrible like that. I overcame this fear by coming to the realisation that being scared is natural but not horseriding and doing something that means so much to me and that I love so dearly would be even more unnatural. I always say to myself and to others that are scared to always know your horse first and never ride if you feel as though you and your horse are not intune and know each other, but if it is only a fear for your own safety then you have to say to yourself that if something happens I will have been doing the thing that I enjoy most in the world!