I finally followed my dreams and finished a game, but instead of elation I just feel tired and empty. Is this normal?

A bit about myself: I've loved games for as long as I can remember. I've been making maps & mods for Warcraft 3 since I got it in 2002, the powerful map editor was also where I learned to code. Last year I finally started to learn to code in Unity, and since August I've been working on nothing but one game which I've just released. This is the longest I've ever managed to work on a single project, and perhaps the first time I can say that I've finished something.

This should be a high point in my life, but I feel more tired than after a 20-hour job.