I use a mounting block (or a stump, log, truck tailgate, horse-in-ditch-me-on-bank) to get on but I often wipe out if I try to get down onto anything but terra firma. Surely you ladies have used or seen the Old Lady Dismount!
1) Order horse to stand still.
2) Reprimand horse for putting his head down.
3) Look down at ground, mentally curse self for cowardice. (repeat 1, 2 and 3 several times)
4) Extract right foot from stirrup, lean forward.
5) Lift right leg over cantle while hugging horse around the neck.
6) Extract left foot from stirrup while shrieking curses at horse, who by now has once again put his nose on the ground. Continue to maintain death grip on equine neck as you:
7) Slither down horse's shoulder to the ground, gouging self in the process with any hardware on breastcollar or saddle.
Done properly, this is low to no impact. Believe it or not, your horse will get used to you using his neck as an down elevator. I am tall and my horses are short but I've seen short old ladies manage this even with tall mounts.