Actually people talk about that feeling all the time in editing circles. The real high is in the making of it for me though, getting lost in the clips. Finishing it almost feels a bit empty sometimes, like the fun part is over. The joy is totally valid, don't get me wrong, but the grind is its own reward.
Totally get that, it's like finishing a book and just sitting there until you pick the next one up. That empty feeling just means you're ready for the next project.