- Exercise daily.
- Eat well. Don’t consume much: caffeine, alcohol, refined sugar.
- Get plenty of sleep.
- Read books.
And seriously consider:
- Speaking to a mental health counselor. They can be heaps of useful.
Alcohol and sugar agreed.
Moderate caffeine intake is largely considered to be beneficial though so I'd remove that from your list. Green tea, yerba mate, and coffee are all healthy beverages for most people. It's important to not drink too much or too late in the day so it doesn't affect sleep, but otherwise caffeine is generally healthy.
Huge meta analysis here. https://www.bmj.com/content/359/bmj.j5024