I like Frenchfit's offering here and second it. I'd add...use some lanacane anti-chaff [or some such] if you don't already; nothing like a good chaff 40 out to make those last miles torture. And the sleep...by all means. A good charged internal battery makes all the difference for me whether I bonk or finish easy. And Frenchfit has another good point too...it IS indeed 'over' before you know it and it is just another 'memory'. That's one thing I always remind myself when in the middle of a big event if I find 'hard times'...that I will feel 'disappointed' and nostaligic when it's over and looking forward to the next one. So...I try and celebrate the 'torture' as well as the 'joy'.
Good luck.