Yesterday was my birthday and I thought it was gonna be a great day, a day to remember.
I was very wrong. At first. Here's my story of how to deal with massive disappointment! The best strategy I know of, the one that is most efficient for me, is disruptive action-taking. Start doing something that is totally unrelated to the topic of your disappointment, and with all your focus, dive into massive action on this other thing. Something that, when you complete it, will automatically bring you great satisfaction and/or joy.