Reddit reviews Nonsense: The Power of Not Knowing

I initially followed the principles of Stoicism, which is a philosophy that's very close to the principles of CBT. So my first resource was /r/Stoicism, where you can find things like this and this that have direct correlation with CBT principles. Greek and Roman literature might be hard to get into, but there are very readable translations and the principles are applicable.

Of course, not everyone is interested in philosophy, so my recommendation would be to find something along the lines of Judith Beck's Cognitive Therapy, or other similar resources that are based on research. I can't really recommend else because I haven't read much from other authors.

But in general I would recommend reading about cognitive biases in general, along the lines of this, this, this, or this. Being conscious of how everybody thinks might help you see some negative spirals in your life, and can help you change the environment that might lead you to that negativity.

But again, professional help can be very useful, so definitely consult a professional who is maybe better for you. Good luck!