Get a full night of sleep. Sticking to a rigid sleep schedule will help a lot with that. Even on days off, don’t stay up late and sleep in. If you want extra sleep, go to bed earlier. Don’t sleep in later.

But also, faking it works with the happier and upbeat part. I remember in high school, most days I’d be tired when I was going in and not ready for the day. I would look at myself in the mirror, fake a smile, and say “todays going to be a great day!” I would actually feel a lot better afterwards and go on to have a pretty great day.