Don't expect too much too soon. At least you aren't waking up on a crowded overnight train with lust aforethought and an oddly wet sensation spreading in your loins as Derek has been known to do. Relax, your body is having a good time even if your mind isn't. Try going along for the ride. Sure, the old nocturnal emission makes a bit of a mess but if your washing machine hasn't spat the dummy from an overload of sheets and PJ's there isn't too much to whinge about.
Wet dreams are perfectly normal at any age.
If you don't make a fuss about your partner's bodily functions then she would be jolly unfair to make one about yours. But please be a bit careful about where you nod off, especially at the beach after a dozen deep-fried oysters. I can't find much that fits. Skirt, East Malvern. Haute couture awaits you.