Take a long walk or go jogging, and meditate after it.
I've been reducing nicotine and caffeine and feeling very depressed because of it. These feelings are related to low dopamine activity in the brain, which brings feelings of inadequacy, depression and suicidal thoughts.
Exercising even once a week will help you a little bit. Regular meditation habit will also help. Its just brain chemistry at the end of the day, and you have the capability to mold it. The problem with depression is that you have less motivation to do the things that will actually make your brain chemistry better, but if you force yourself to do it then eventually you'll feel better.
Also in addition you want to avoid things that actually reduce your dopamine baseline. Porn, masturbation, drugs and entertainment will increase it for a while, until the receptors become numb and then your baseline drops.
