Its a normal thing Rich. The GM's give up on weekend tournaments in their 50's. They play just as well as ever in the first several games and then wear out. Maybe you're playing too many games or at too fast a time pace?
CHESS USED TO BE FUN FOR ME . . .
I'll be honest with you....After reading this, you're a damn inspiration!
Chess and other passion interests is quite wonderful.

I hear ya! After thousands of games and years of competition things sometimes get old. I don't study 3 hours a day anymore either. Hardly ever go to tournaments. My thing now is Brazilian Jiujitsu and it scratches that same itch while giving me abs. But in my own personal experience, having a casual approach now has let me reengage with it an even have fun. Sometimes you just need a break. Even a really long one. Much love!

I am also doing Tai Chi lessons once a week.
Piano lesson once a week. Both are fun.
In one of my GAMES I lost a Rook a BLUNDER . . .
When I met chess in 1952 it was fun. Only one friend took to it. I met George Koltonowki blindfold champion. Joined his club. It was fun. I could play blindfold chess with a friend so we wouldn't be fired if we were caught playing chess.
Played at San Quentin prison it was terrifying. . .
Great fun. Taught many youngsters to play chess and ran tournament s as director USCF.
I WAS PAID TO TEACH GROUPS BY SCHOOLS LIBRARY, IT WAS FUN.
SLOWLY I GOT OLDER AND OLDER AND IT SEEM I AM NOT HAVING SO MUCH FUN. ONE DAY I was going to teach at a LIBRARY group I ended up in the hospital with a heart pacemaker. It stopped being so much fun.
Chess.com rating has been going down and playing very clumsy it's isn't more fun any more.
I had 24 club chess sets I began to give them away. The clocks the demo board I can't find a younger person to give to.
Several of weeks ago I was offered 30 more club sets, 20 chess clocks and 30 vinyl chess boards for $20:00. So I took them now that was fun . . .
March 2 I am going to help the library run a chess program for teenagers. FREE! I hope it's fun again.
I'm 87 years old still looking for fun.
Still I bowl in three leagues every week and I'm having fun there. . .
Here is my profile link . . Click on it .
https://www.chess.com/member/richcolorado