When I was in my twenties I would often get only 4-5 hours of sleep in a night, or sometimes if it got to be about 4am I'd just stay up through the night and go to sleep at 11pm or so the next night (early for me). I don't think I would ever have called it "euphoric," but back then it was a mildly pleasant experience to be on the edge of tired/exhausted.

Now not so much. Although I still stay up later than I should sometimes, these days getting 3-4 hours of sleep feels about the same as staying up all night once did.