BUT, posting downhill is my enemy.
Even on a very shallow incline downwards I'm allll over the place. If I try to post leaning backwards slightly (aka, if there were no horse I'd be upright, etc so not really "backwards" but it feels backwards), I find myself falling back into the saddle really hard. If I try just posting normal, I end up leaning forward over Lacey's neck and that can't be correct since my weight would inevitably encourage her to be on her forehand, and being on the forehand + going downhill = bad.
I do know that I do/did grip with my knees something awful when I post and I think I've gotten that fixed on flat ground for the most part. Going uphill is a little harder because her trot gets HUGE going up and I find myself gripping away with my knees, but I think I'm getting it (grabbing mane is my friend, haha).
However, downhill = evil.
Are there any tips or tricks I can try?
I'm riding in an stock saddle, if that's important to know. Also, Lacey's trot is certifiably "unsittable" (she makes ANY other horse feel like they have the flattest, smoothest trot ever) so there's really not the option of sitting. I've been coping by asking her to walk down hills but I'd like to try trotting down the non-scarily steep hills we come to, at some point, because I'm sure it'd be good for her (more thinking and all).