Hey, I remember you! Welcome back :-)
I haven't rock climbed in years now, (but don't want to "quit", I just don't want to do all the training...) and I'm sure I would feel the same way if I went out climbing on a familiar crag now.
I think the best advice that would work for me would be to not do the exact same things I did earlier, if possible have your focus a different place from where you used to. If you used to go for regular training rides of a certain length, try to see if you can find completely different routes. Or commute, or run errands by bike, or go to different places for a purpose, to shop or take photos or watch wildlife. Or try trail riding, or running, or swimming instead. I'm thinking that the point is the total amount of exercise your body gets, and you know it'll be a long haul, so you might as well keep yourself entertained and see new things on the way :-D
I hated starting to run, because I ran the same stretches that I rode my bike, and it felt like I was standing still. Now I run a route that I keep myself from biking, one that I actually can't bike because of steps, so I can still feel "fast"... Now I enjoy feeling more versatile, but it took a while. For a while there my only sense of achievement was that I actually had run that day.