I know exactly what you're talking about.
I was very fit in my twenties, then got badly injured and sort of got very unfit for about ~7 ish years where my focus changed. I recently got back into mountain biking, and the first few hill climbs were confronting to say the least. Literally me lying on the ground holding my chest, and ego thinking "What the actual f--k". The real motivator was having dropped kinda large cash on a new bike. I didn't want to let myself down and quit.
If the op has a similar vocation, I'd lean into that stuff. gently, gently of course.
Getting your lungs into MTB shape is so painful (both physically and mentally). Now that I have the fitness, keeping it is extra motivation on top of the pure joy I get from going downhill right on the edge of control. Having a group of friends who also enjoy the same things is also huge for me. We encourage each other to get out more and it's always more fun to ride with others, even for a solid introvert like myself.
Can't go wrong with Giant. The only thing I really noticed over the last decade is how much bigger bikes are. My Production Privee Shan 5 dwarfs my [large size] Orange 224. Back in 2010 the 224 was a beast!
Yeah my memory is of riding dual suspension with 26 in wheels with 2.1 wide tires. And now I'm floating about on 2.5inch maxxis on 29 inch rims. It's crazy what I can just roll over on a hard tail that used to buck me off.
