Y does my horse always trip?

Brief：
I have a 24 year old morab and when I ride her she is always tripping. She has been shod lately and there is nothing health wise wrong with her. So I .. 

Dang, brain fart!

I'm getting my text books, hold on... Make sure that the shoes are fitted properly, and that her hooves aren't too long. We have had a few farriers who rush, and screw up a horses motion.

If that is not the case, maybe it is a joint problem, or it could be that she isn't paying attention.

I would reccommend getting your vet out to check her, just to be sure there is nothing more serious behind her tripping. maybe the horse's shoe is already wornout. have someone take a look on it and replace it asap. I am curious, is she tripping in the front or back?

Usually chronic tripping is a sign of lameness, particularly at her age. She's definitely unsound (not necessarily outright lame)... Even if she's not paying attention, she should be stepping up enough to not be tripping in a level arena. If she's not throwing her head around and looking all over the place, it's probably not a question of imbalance caused by inattentiveness... and that sort of behavior I wouldn't expect from a 24 year old anyway. If you ask her for more motion, she will pick her feet up a little more but that doesn't help you solve the fact that she is moving unnaturally when going at her own pace. Any chronic tripping is at the very least improper movement which could stand some correcting.

If she's tripping in the back try having your farrier ease her breakover next time she's trimmed so that stepping over her toe and pushing off is not so difficult for her. Worked wonders for my mare when she started tripping in the back due to arthritic changes.