This has been a little interest of mine recently!
Back in Jan I had laser eye surgery, a year before I had a rubbish sleeping pattern where I'd wake up after 4-5 hours sleep. Fully awake at the time but I'd start to crash later on in the day. After surgery it's standard practice to be given a sleeping tablet to help you recover. I had the best nights sleep in ages! So I started to get OTC sleeping pills for nightly use. But I found some times I'd be more tired during the day. Since Jan I've been into coffee and I'd have an espresso every morning.
But just in the last few days I've stopped having it and yeah, I feel great! It's really relaxing and I feel at peace with loads of things I would normally be irritated about. I feel happier.
Before all this I used to get 7-8 hours sleep a night and would wake up with boundless energy to the point I irritate my gf by jiggling my legs sat at the desk, heh. So maybe that morning energy was always there.