After my horse Honeycomb passed away (who I'd had from the age of 12 'till I turned 30) I thought I'd never ride again. Even catching a whiff of horse-and-buggies in Central Park from a cab made me melancholy! But, wouldn't you know it, on a bright Fall day three years later, I woke up and wanted to ride.
So I called the woman who owned the stables where Honey had lived and asked if I could come out and ride one of her school horses.
I got on and.....it all came back. Everything from the bad habits I had accumulated during the years Honey and I stopped showing or taking lessons to my velcro butt. By the end of the ride I was cantering around, grinning like a fool. Of course, I was definitely rusty, and later very sore! But since then (4 years), I've been riding very consistently (4-5 times a week) and earlier this year started took a huge step (for me) and have begun Dressage lessons again. I even find myself entertaining the thought of a schooling show. Which is crazy talk, since had I vowed to never show again after my last trainer/experiences. Just goes to show what time does, right?
Anyway, the bottom line is, like everyone else who has commented, riding a horse has been like, well, riding a bike! Your body never forgets. Just be warned - your horse-fever will come back with a vengeance! Mine simmered down during Honeycomb's later years (she was 27 and had Cushings - not much riding toward the end. Just lots of love, grooming, carrots, and hanging out). Then, when she died, I was so heartbroken and sure I'd never ride again that I gave away all my tack and equipment. But now...I'm as totally horse-bit as before. As evidenced by the fact that I am on this forum instead of working! HA! Good luck, have fun, and don't be scared. You'll do GREAT!