I'm 40 and It's been about 10 years since I gave up the hard training.
It's tough to give it up and it took me several years to find the right mix of diet, cario and trips to the gym. For whatever reason I've completely fallen in love with lifting weights over the years. Not a bad thing but I went from a 160lb racing weight at 6ft 2in to 205lbs now. I put a ton of effort into diet so I'm remarkably lean and it certainly wasn't a overnight transformation.
I think I have loved lifting so much because it's a newer challenge. I can still hit PR's. It's very motivating and fun.
Anyway, my routine and goals change from time to time but I'd say a typical week looks something like this.
2 runs of 4 or 5 miles
1 to 2 hard interval sessions on the rowing machine (bought one for home). Typically, something like 10 by 30secon/30sec off or 10 by minute on/minute off. 10min warm up. 5min cool down.
3 to 4 days a week lifting hard at the gym
a few hour'ish walks with the wife and dog at night
The beauty is that I'm training for fun at this point. If I get tired of one thing I'll take a few weeks off and do more of something else.
That said, It's still hard losing the identity you've formed over your lifetime of training balls in the name of running fast.
Good luck.