"So why exactly are morning people so happy and feeling so healthy? Well, it probably has to do with the fact that they're not constantly having to fight their natural tendency to sleep late. The world, as you may have noticed if you've spent any time living in it, is heavily oriented toward morning people. We have to get up early, get to work on time, and then actually pay attention once we're there. All of which is much easier to do if you're programmed to wake with the sun—or at least to wake up alert instead of sitting in a fog for the first few hours you're awake like most night people do. Forcing yourself to fit into the morning mold can be tough, says Biss: "An evening person may go through their week feeling unhappy because they have to get up earlier than they would like to." Indeed, it is enough to make one quite pissy.
Also, night people might not be getting the right amount of good sleep since their bodies are meant to be awake for part of the time that society tells them they should be sleeping. This is also known as "social jet lag," since your internal clock is out of sync with society's clock. As previous research has shown, not getting enough sleep can have serious consequences for your health and immune system. And if you feel tired all of the time, you're probably not going to describe yourself as filled with joy.
So are night people just doomed to be miserable until they get older and magically turn into morning doves? Pretty much."