My boyfriend's schedule and mine are so opposite it isn't even funny. When we are together... we try to have as much fun as possible. Sometimes, he does want to be intimate when I can barely keep my eyes open. I've told him a few ways to wake me up nicely (soft kisses on my face, etc) and I've learned that I usually feel so much better afterwards that it's totally worth it. Maybe he can do something sensual that you really like to get you more in the mood or maybe reassuring yourself that in five or ten minutes you can get so into it. I hope it all works out!