The human brain is a pattern-matching and feedback system.

Positive feedback can send it spinning out of control or pull it out of extremes when coupled with negative feedback. Negative feedback can keep it running in a healthy range by moderating its actions. After a routine is developed with good mental health, performing any of the actions in the routine will help stimulate the brain to emulate the old pattern, maintaining mental health through conditioning.

As I wake up each morning, I check in on my mental state -- alertness, ease of waking, how tired I am, how my body feels. Having a baseline for the day helps. If it's a change from previous days, I look for causes. If it's a positive change, I try to do that action a little more (positive feedback). If it's not, I try to not do that so much (negative feedback).

I eat a good breakfast. Blood sugar levels affect cognition significantly when they're out of norm. I'm hypoglycemic, so dietary choices are doubly important to mental functioning for me. If my blood sugar dips too low, I tend to be super emotional and if left unchecked, manifests as depression. I eat regularly though the day to maintain things.

Excercise helps release endorphins that can help stimulate peak awareness, though usually with a fall-off that leaves one a bit less energetic than baseline.

Regular excercise negatively feeds stress reactions within the body, which helps raise clarity of thought, and makes the brain react to the stimulation by jumping into the clearer thinking mode earlier.