"In health care, self-care is any necessary human regulatory function which is under individual control, deliberate and self-initiated."
For n=1, I've struggled with (manic) depression and anxiety most of my life. And while I've used a variety of strategies to cope (Seligman's "Learned Optimism" and a potpourri of Buddhist ideas were incredibly helpful), the secret sauce was getting off of sugar and junk food. When I'm staying on a whole-foods, keto-ish diet, mood swings and unwanted negative thoughts have their volume is turned down by 90%, making the remainder relatively easy to process.
Everybody's different, so YMMV; in some cases, medication are an appropriate tool. But there are some universals that basically benefit every human: drink more water, get more sleep, go for a walk in the sunshine, eat your vegetables, and the less sugar (probably) the better.
All medical interventions should include the no-brainer diet, vitamins, exercise, self-esteem interventions.
That's a very strong claim to make so nonchalantly and confidently without referring to a source.