"Just keep going"
It's simple but it usually does it for me. I admit that it allows for overtraining, but when I'm on the mats I try not to think about how long I'm going to be there, or what's waiting for me and focus simply on doing what I'm doing right then.
When I powerlifted it was Dynamic Squat days for me, all those sets and little rest. I had my training partner count and focused only on the set at hand until they were done.
On the mats now if I'm in class I focus on what I'm doing right then and not "how am I going to make through", on open mat days I go for the time alloted and try to focus on the present.
I admit there are other factors: ego/pride, respect for my instructors and training partners, but "just keep going" and staying in the present builds upon all of these other factors.
Just think about what the lions den trainees had to go through.
First of all I always take a second before I start any set to promise myself exactly how many reps I will do. Then during the set, I think about how I set a simple fucking goal for myself and I can't let myself down in this. I imagine cowboys and soldiers and lumberjacks and coal miners back in the day who had to do much, much worse **** than those last twenty pushups or whatever, and I basically use a one-two punch of keeping my word (to myself) and shame of my failure to reach the masculine ideal if I don't do it.
Works great! Music also helps.
Oh man, and while jogging; I live several blocks from an old cemetary, it's the exact halfway point in my run. So when I pass it, I have my running playlst timed to switch to zombie movie music, and when I run back home I imagine a horde of zombies rising from their graves and shambling after me, it is fucking AWESOME, because it not only works but is also just damn cool.
One night when the zombies actually rise from the dead, Ill be fucking SET.
I live near Highgate Cemetery (where Karl Marx is buried and, yes, he's still there) and used to run past it until I thought about my coughing my lungs through my nose whilst those other unfortunates were unable to - so,.....I changed my route.
PS. Halloween always draws the nutters....