Right now you have a golden opportunity to analyse the ways in which you level yourself, play badly and spew when you are playing and not playing your A-game. This mini-grind operation is likely to show examples of all the absolutely worst thing you do while playing because you have been playing under a new high of stress.

One way to stop leveling yourself I think is to learn to recognise when it's happening and catch yourself. This may be in the spirit of cognitive behavioral therapy (I remotely have a laymans understanding of what that is) - by that I mean recognise the thought patterns that lead to the actions that you are trying to avoid. A perhaps related way is to look for more overt signs - once you've spewed off a hand instead of "burying" it as the proud ego will try to do so as not to admit having done something stupid, take a moment to reflect analytically if that hand was well played - and maybe implement rules for how bad a play you allow yourself to make before you take a forced break to get your head straight.

I don't have good habits around this myself, but it's akin to having a preparation routine that gets your mind in the right mindset to play the A-game - and when you recognize the A-game is off, just stop, clear the head, do the routine again, then sit back down.

In other words I think the way fix the self-leveling leak is to play your A-game more of the time. Tilt management.