I’m regressing in chess big time. I’m like worse than average. What happened?

One thing that happened is that instead of keeping on doing the things that helped me improve, I stopped doing pretty much all of it in favor of doing things that I KNOW aren’t good (exs. playing when tired, playing short-time games). Why do I do this with chess? Or exercise? Or diet?

It’s so frustrating to do things, see results, and then…just stop. Why do I do that?

I wonder if part of it is just sabotaging my progress. Even if it’s not that, intellectually I know changing inertia is harder than going with the flow. Why am I always insisting on starting and restarting and restarting the same things?