Well, if you're concerned about loss of energy, I'm guessing you have rough burnouts. You don't know what kind of stuff you could be doing (although I have the same job, it's pretty low-level but does get tiring).

If I were you, I'd hold off. Here's what you do:

Do something else tonight.
Go to work tomorrow. Work hard.
Come home, kick a niiiice session, you've earned it. :dance: