You are most likely to suffer from insomnia if there's an important reason you must get a good night's sleep. There's nothing like a little pressure to ruin your relaxation. Maybe you should go with plan B, but that has its own dangers- a couple of drinks or a sleeping pill might help you fall asleep, but they could also cause you to oversleep in the morning when you have to be at your best. Then that exam, job interview, or flight could be endangered. I have no trouble taking an afternoon nap most days, but if there's something I have to be ready for at a particular time afterward, I know ahead of time that I'll just lay there and watch the clock. This is the latest comic from the Awkward Yeti.