None of this constitutes medical knowledge, just 17 years of personal experience:
Basics
Do you live in the US? If yes, look around your city/state/county for sliding scale mental health therapists. If you're bad off, they can set aside your fee. Google can help with finding them. 1-800-THERAPIST Most larger areas have some sort of help, while more rural areas tend to lean towards faith based counseling. Getting perspective on your issues from a trained professional is the best next step, but in the meantime, write down the things that used to make you happy, and try to do as many of them as you can budget allowing. Make time, even if that means getting up early. Get more sunlight. It helps you feel better, as does general exercise. Volunteer to help other people in a weekly or daily commitment. Helping others can distract you from your own pain. Get enough rest. Sleep is important, and you can take a mild sleep aid to help. You should also rent this book from the library: "
Feeling Good: The New Mood Therapy." Dumbest name ever for a good book to bootstrap yourself out of bad moments.
Hard Times
If you have a rough spot, recognize that your emotions and their causes are temporary, and not really based in reality ( I don't have any money, so I can't buy my kid ____, I'm the worst parent in the world etc) and just step back from them as they happen. Busywork helps with the hardest hours, and being with caring friends and family helps fight the tendency to isolate yourself, which further worsens depression. Avoid alcohol, and drugs, as they have a tendency to act as "downers," and your money is better spent doing something else.
Dark Moments
If you find yourself in a recursive hole of pain, and are facing a decision with permanent consequences, call someone. (If you are alone, call 1-800-999-9999 ) Talk with them about this issue, or don't, but do talk, and give yourself time and distance to rationally think through a decision you would regret. Sleeping on any major decision like this helps put it into perspective, and no matter how bad it gets, there is always a better option than taking the choice made mid despair and pain.