Spooky at faster gaits

[LynOlds@aol.com]

I need some advice please. I am planning on doing a 25 mile CTR in 3 weeks
with my half-Arab. My problem is that he tends to spook at things on the
trail. At the walk he just looks at scary things, but at the trot he jumps
sideways. At the canter he will spook sideways hard and switch leads in back,
almost unseating me every time. Sometimes he will actually stop and I end up
on his neck. He is quite fit and the problem seems to be getting worse as he
gets in better shape. I try to stay calm and do not punish him, but I am
afraid that maybe I will get tossed. He has a wonderful ground covering trot,
but now I find myself trying to hold him back because I'm afraid he will spook
at something. He does seem to get less spooky after about 45 minutes or so of
riding. Does anyone have any suggestions for me? Thank you very much in
advance.