Mine are:
More exercise than you think you need. I work out with weights and HIIT 3-4 times a week, do a 2 hour yoga class and go for walks too. My energy has increased a fair bit since doing this.
If you are in UK, use a Vitamin D spray from October to May.
I also take an iron supplement, and if I'm run down, a multi vitamin too.
Do small things every day that give you a little lift - make a cup of really good coffee in the morning, feed the birds and watch them as you drink the coffee, put on favourite music when making dinner or folding laundry, watch a comedy sketch, run a deep Epsom salt bath and lie in it, reading a book for 20 mins.
Always have something to look forward to: immediately, very soon, this week, this month, this year.
E.g. Immediately - a cup of coffee after completing a task at work
Very soon - a favourite exercise class this evening, or a catch up on the phone with friends
this week - a night out with your partner or day out with family at the weekend
This month - a gig or weekend away
This year -a big thing like passing an exam or moving house or a trip of a lifetime or running a marathon - the stand out thing of the year.
I think those things give you energy as they propel you through life with lots of stations along the way to look forward to.