I'm 56 and would have said the same, only you said it first!58 and strangely enough started doing a lot more wrenching on my own cars in the past few years. My body is not beat up like a lot of guys I know. I started working out a few years ago, that has made a huge difference. So feeling good and still enjoying wrenching (on my own stuff, occasionally!)
Now that I am retired, I take my time with car work, I do more of it and don't feel rushed. Problem is, with 2 very reliable cars there just isn't all that much to do.