It's all part of the process of healing brother.
The first step is identifying, acknowledging, and even communicating the emotions that are coming up, which helps us find out where they are coming from. You've been doing this for quite some time; I watched it in you back when I just subscribed to Anarchast, and I've seen it more clearly as I've gotten to know you better.
It's easy to think that you've fixed your depression when you are on a streak of eating right, staying clean, and communicating with loved ones, but there are always going to be low points as well. In the sine-wave of our lives, there will always be peaks & troughs. The process for me, has been of elevating & balancing the wave so my highs and lows get less extremely different, and are both a little higher each time.
When those troughs come, it's important to keep moving forward, get back on your mindfulness of body and what you put in it, keep asking for support, guidance, and healing, and realize that those are the opportunities for the most trauma to be let go, and released from your field. Sitting with the sadness, not being attached or judgmental of it, just observing it, feeling it, letting it pass, and giving thanks for its presence and the lessons it brings.
These waves of depression (in my experience) are generally ripples from some old trauma, and by feeling the pain, we let it flow through and pass from us instead of fighting/ignoring/fleeing and keeping it around to come up again & again.
I would love to talk when you have some time, I'll reach out of FB. I'm hear to listen, and I've got quite a bit of personal experience & tools for I've found for this healing journey (the most important part of our activism IMHO).
I HIGHLY recommend reading Radical Forgiveness, it will help. Even just the story at the beginning ("Jill's Story", not the foreward) is quite powerful & healing on its own.
I love you brother
Remember:
You are beautiful
You are powerful
You are free