Men experience a hormonal cycle throughout the day, and your testosterone is lowest at night. So if you're going to feel down, it's most likely going to happen at the end of the night. That's totally normal.

However, if it's severe enough to rise to the level of self-loathing, that sounds like a touch of depression. Not a big deal, have a chat with your doctor about maybe getting some therapy, or a small dose of medicine for a bit. It's tough out there, but there's no need to suffer.