We are all a complex feedback loop between genetic presets (temperament), our environment (physical, social, biological) and the sum total of this loop running up to this exact moment. We all have a personal history. This implies we also have habits of thought, emotional reaction, and physical behavior, acquired over time.

It seems to me that I have some learned fears and coping or defense mechanisms which keep inadvertently getting in my own way. This is, I believe, what causes my excessively negative mood states. I have come to this conclusion based on several decades of meds, therapy, reading, journaling, trying all kinds of things. I believe that there is no one specific treatment that is right for everyone.

I agree, there is always a "reason why". The first order of business is to define the actual problem. All too often, our conscious minds are not as completely self-aware as we like to think.