Jocko Willink is a beast. Former Navy SEAL and now likely one of those mental/performance coaches.
It's pretty simple, no excuses. What do you do on the days where you don't feel like working out, doing your best work, brushing your teeth, ...
"I do it anyway."
It's likely just the little voice in your head and you will be happy after.
So, do it anyway, go through the motions!