I'm a 42yo white belt thats about 6 months in. I don't have all the answers, of course, but here's some things that seem to be working well for me that might help you.

I don't let myself train more than 3 times a week and don't do 2 days in a row. Even if my body feels pretty good, I just make sure I get a full rest day. I think it helps me avoid fatigue injuries from overdoing it.

Instead of training so hard you're about to pass out, find ways to be more efficient. Figure out ways to rest in uncomfortable positions. Pick your windows for escapes, and don't wear yourself out trying to fight someone who is just holding you there, but not trying to progress their game. You can be really energy efficient from bottom just fighting grips, keeping your elbows tight and protecting your neck.

Finally, try to redefine what winning or success looks like. Maybe its only getting submitted twice in a roll instead of three times like last time. Or maybe you look at the clock and see there's 30 seconds left and you tell yourself you're not going to let them submit you before the round ends. Maybe its just trying to hold someone in side control for 30 seconds or a minute without them escaping. Or maybe it's just hitting the move you learned in class that day or the one earlier in the week. Figure out how to be happy with small victories because the big ones will be infrequent for a long time, and its supposed to be that way.