I've battled depression for close to 40 years. This is what works for me most of the time.
1) Exercise - EVERY day (minimum of 20 minutes)
2) Stay on my meds - even if it seems they are not working or I don't really need them anymore (this has been a buggar as I don't like feeling dependent on something to make me feel better)
3) Get up at about the same time each day and go to bed about the same time each day. We really only need 6-8 hours of sleep a day.
4) Talk to someone who will accept you and not pass judgement (just a great listener - "Tell me more" type responses) 5) See your doctor - preferably a Psychiatrist as they specialize in medications and how they interface with the brain and work to rectify affective disorders.
6) Avoid other bummed out/negative people like the plaugue. They may be your best friends but you need someone who is neutral at a minimum right now.

Anytime I don't do the above I slip - I slip anyway but the above really minimizes the impact.

Steve