I agree the hardest part is the ground. Biggest lesson I have learned, don't canter/gallop up a hill if there are gopher holes.... your horse WILL go down. Looking back it was pretty funny (mostly because we both came out fine) but my horse tripped in a gopher hole, fell and rolled onto me. How I got out of that one without a bruise, I have no clue. I felt so bad to my horse that I got off and hand walked her the 10 miles home.
Remounting. The trail I usually ride at has really nice mounting blocks that are just perfect for old, short, heavy people like me - I can just swing a leg over and slip into the saddle, no muss, no fuss, no straining for either me or my horse. Unfortunately, they are only at the trail head. The trails themselves are kept clear of debris, so there are no convenient tree stumps I can use. I tried using the side of a ravine...that turned out to be a disaster!