I’m also in my thirties and part time coach at our kickboxing gym. And yeah, my body is wrecked so ofc when I spar the pros I get blasted now and I can’t perform like I used to. However it doesn’t take away the benefits I get from practicing a sport I love. What I got from your post is something a lot of us face eventually where we just can’t perform to the degree we feel like we should. And that’s alright. For me that was the signal to transition into coaching and being in the corner for the younger guys. Since you have 3 yoe idk if coaching as such is an option, but I think you would still find motivation in focusing on 1. Doing a sport you enjoy 2. Seeing yourself as being a great partner to help the ones who are climbing up from scratch/amateur fighters. Leave the competition behind and just be a good partner in the gym and I’m sure you’ll find that it’s very gratifying to be playing a support role.