It's awfully disappointing to go out of your way for someone and feel unappreciated. You don't have to send a thank-you note for every orgasm, but it doesn't hurt to show some gratitude or admiration of a job well done. Flattery is helpful when it's deserved. If a partner made you feel particularly good, say so! A little compliment (or just a "wow!") goes a long way. Positive reinforcement is your friend. If you want it to happen again, show some appreciation and get the message across.