I look at it more from the perspective that I'm giving myself to these different things, like a jug of willpower. I only have so much to pour around and once at the limit, that's when the drained, lethargy, burning out feeling happens.

The activities aren't draining you, you've just spent what you had. Using all that willpower to 'shapeshift' yourself to how you think everyone wants to see you pretty much leaves you nothing from the get go.

We're all the center of our own universes, our brains default context is centered around how stuff impacts you. Everyone is like that though, so when you think you might be judged, the people you think might have noticed probably have their own little insecurity going.