Unfortunately depressive rumination can become self-referential -- that is, while you might be more analytical and capable of coming to extraordinary conclusions about things, that analysis can easily turn against you and become self-criticism about your competence to produce anything meaningful. It's a double-edged sword.

Good luck. I did some and found it helpful. I kind guess personally that it works by a kind of neural network rewiring. Before CBT some neurones are taking input, processing it as indicating things being crappy and directly signalling that to the older reptilian bits of the brain that deal with that, without conscious awareness. By consciously becoming aware of the things are crappy reasoning you can argue against it and rewire those networks. At least that's my theory on it.

That's essentially mindfulness too -- you catch a negative thought and then you construct a counter-argument against it to placate the reptile-brain. It's like living with a little child who's prone to temper-tantrums. Whatever it can take poorly it will, and it's your responsibility to re-frame things in a good light quickly.

But mindfulness is not about re-framing or answering back with an argument. Its exactly the opposite!

+1 for a combination of both CBT and mindfulness. Both have really helped me with my depression.

Get out into the sun. I don't know why, but something about about getting a minimum amount of sunlight (hour?) every day improves my mood immensely throughout the rest of the day. The Seasonal Affective Disorder is real

So is vitamin D deficiency. Get some sun (or pills)!

From what I understand (maybe incorrectly) vitamin D supplements cannot make up for the vitamin D one would normally get from sunlight.

Our bodies don't process it in the same way that makes it useful to us.

Which is a shame because I spend 90% of my time indoors.

I don't like to think about the spirit/mind/brain being "broken" in case of depression. Depression causes problems, but often the only way to get rid of the cause is to alleviate the problems.

Everybody, including those described to be mentally healthy, can and should improve and evolve their mind, and CBT can be effective for that.