Tired? At the end of a long day? Or falling down because you haven't slept for three days? Just how tired do you think you have to be before the "range officers" tell you to go home?
I'm tired everyday, and I don't think the BGs are going to wait until I'm refreshed and ready for "safe" action after a good night's sleep. You have to be able to defend yourself regardless of if it's been a long day or not.
You might not punch out the ten ring at the end of the day, but you should be able to score nines without shooting the guy in the lane next to you.
Now if you just don't feel like loading up the gear and driving to the range, heck, we all feel that way sometimes. Sometimes the lawn doesn't get mowed either.