What you are describing is mental. You are losing focus when you start counting your score and placing an expectation on your round. Play one shot at a time and don't add your score. For me, I know when I am even or one over, but for some reason if I add it to the expectation of the unplayed holes it puts a level of stress that I do not need. Staying with one shot at a time focus provides me the best results and keeps me in the present. Easier said than done, but once you really stop putting a premium on the outcome, you mind frees your body to make the best swings.
First, welcome to The Sand Trap! There are tons of different sections here with a lot of great advice.
When you say you start to make dumb mistakes, what do you mean by that? Course management mistakes, mistakes in your swing, etc.
If it is course management mistakes, I highly recommend reading the book called "Lowest Score Wins" which was co-authored by the owner of this site, it goes in-depth into course management and might be helpful if that is an area where you are costing yourself strokes.
If it is a swing issue, it sounds like you went through a pretty big swing overhaul, so it's possible that your new swing just isn't 100% ingrained yet and at times you might start drifting back to old habits.
One piece of advice I have is try to develop a pre-shot routine, something that takes you out of the relaxed mindset of in between shots and one that gets you focused on the shot at hand. Once your pre-shot routine starts, the only thing that should matter is how are you going to execute the specific shot that is right in front of you. Not your overall score, not if you are winning or losing in a match, not what you are eating for lunch afterwards, etc. Then once you hit the shot, then you can relax a little, but for those 20-30 seconds or whatever, 100% of your focus needs to be on that shot you are about to hit.
Another thing that could possibly help too is to either not add up your score until the very end of the round, or if you start adding the score up mentally when you look at the scorecard, have someone else in your group, preferably someone in the other cart keep your score so that you can't even be tempted to look at the scorecard mid round
Bryson is just asking for more "Brooksie" at this point. I am not sure how this really helps him in anyway to keep participating. How can this not spill over into the fan base with this sort of outward trolling going on? Let your clubs do the talking.
I am waiting for him to say, "I have a fever, and the only prescription is more Brooksie!" 🤣