I get up at 5am to practice for a couple of hours. At this time I'm sober and I do all the serious disciplined stuff, Bach and scales and arpeggios and any pieces I'm learning.
Then in the evening after 9pm I sit down again, this time with a glass of wine, maybe something else, and play purely for pleasure - anything I feel like, stuff I'm good at, stuff I love like Chopin etc, don't stress too much about technique blah blah.
I have a break every half hour or so, top up the glass, have a ciggie break. Keep going until I fall off the bench. he he. Well perhaps not quite so bad but that's the general idea.
Not surprisingly I play better in the morning. But I have more fun at night.
If I was a performer (which I'm not so it doesn't matter) I'd always play sober and straight.