I started at age 62.
There was a very minor psychological adjustment in having to take daily prescription meds. I never have before. But I quickly realized that I was probably the only 62-year-old in Nova Scotia who didn't take meds, so no big deal. I take my spiro daily, so it quickly just became part of my daily routine. I take my E by patches, which last three and a half days each, so remembering to change them is a nuisance. I sometimes forget and have to do it a day late.
The physical reaction is entirely positive. My only side-effect is low blood pressure from the spiro. I manage that by drinking lots of water and not standing up quickly. The intended physical and psychological effects have been great. I'd be happier if my boobs would develop more, but I may have hit the end of the road there.
My quality of life is 1000% better than it was! I feel whole in a way I never did before. Most of that is probably attributable to RLE, which I started three months after I started HRT. The hormones definitely help, though.
If you are truly trans, you will not feel awful. Because of this, some therapists use HRT as a diagnostic. Most doctors will start you on a low dose, with frequent monitoring of blood levels to ensure that you body is tolerating the meds appropriately, before increasing you to a full transition dose.