Here are my quick answers, subject to frequent change:

#1 - Sleep
#2 - Maintaining a daily routine
#? - Anti-anxiety medication
#? - Avoiding stress
#? - Selective, limited engagement with the world and society

As much as I want to add "diet and exercise" to this list, and I do have diet and exercise regimes, I have not - in my case - found them to be significant relievers of depression-anxiety.