Just like the Paul Sheldon character in Stephen King's Misery, I have my own little ritual when I finish a manuscript. I'm sure many writers do. Much tedious work remains--finding a publisher, for starters--but with all the writing done I can take a few days off with a clear conscience.
Sheldon had one drink and one cigarette as his celebration. I wait until I've made every improvement I can; only them do I type THE END at the bottom.
What can I say? I'm a hedonist.