This is totally normal. A lot of times things like depression just show up out of nowhere. Basically what happens now is you teach yourself a new way of living your life. You take stock of things you eat and remove triggers. Caffeine is a big one. I noticed a huge increase in my mood since I've stopped consuming caffeine (and ironically more energy as well). Fish oil vitamins have helped me as well.

You also take stock of your limiting beliefs and insecurities, and challenge those beliefs.

And then there's accepting that it might not ever go away, but when you stop resisting it, the storms pass rather quickly.