Wallow,
sometimes the environmental surroundings of a childs unbringing, which may or may not be combined with other factors such as genetic predispositions or certain life events, can facilitate the development of a mind which almost automatically turns to depressive perspectives. The glass is always seems to be half empty. Many parts of your psychology and thinking are influenced by your environment, we are all like this and you would be highly abnormal if you wasn't. So I do
not believe blaming yourself for negative thoughts is an accurate perception of reality, but it is an obvious perception arising from the depressed mind.
I was raised by a mother who is perpetually pessimistic. She almost always sees the negative view of everything. I learned, indirectly and directly from my mother to think this way. ''I would never get a good job, I would never have any money, good things don't happen to me, only to others, I lack the skills that others have, I will fail at the things I try, etc etc'' It was pointed out to me that I had this negative mindset by a friend at university, I had never even realised that there was a problem with the way that I thought, I hadn't yet learned that perceptions are not always realistic.
I now work in academia, because of my studies in science I often think about things in a way that I never used to and in a way that most people do not. My thinking about the natural world changed with the experience of learning, the environments it has exposed me to, and the career challenges I have had to overcome. My system of thinking is constantly evolving as I learn to adapt as efficiently as possible to the world in which I wan't to live.
We all have ingrained ways of thinking and sometimes these thinking patterns are maladaptive, such as when we constantly see the negative side of things. But this is not your fault in any way. Its just the way you have developed due to your environment and due to your neurochemistry. You can adapt and change just like we all can, as this is the nature of psychology. You are already thinking about the nature of depression and what it is, so you are already in the process of trying to overcome this problem. This shows a willingness to challenge your negative thoughts, and so you should be praised rather than condemned.
With the help of CBT you can learn to challenge your automatic negative thoughts and contemplate the more positive aspects of lifes events. I do this every day and the more I do it the easier it gets. I hope I never stop doing it.
I do not know your medical condition, but for me I also have clinical depressions that occur due to an illness that effects how my brain is functioning. You may have a clinical condition severe enough to be diagnosed with major depression, it is definatly an illness. Alternatively, you may be going through a difficult time in your life and your brain isn't releasing the chemicals how it usually does when you feel happier. Perhaps you have dysthymia, which is a less severe form of depresion but still bad enough to be considered a clinical problem.
The bottom line is, if you are experiencing mental pain, depression or anxiety for an extended period of time, ranging from weeks to years or even most of your life, you are suffering from mental illness.
CBT could help your negative thinking pattern, medication may also be an option.
I have depression, I thought I was a week feeble looser, now I am proud for living with a condition which I did not ask for and I hope soon you will be proud to have experienced the kind of mental pain that most of us do at some point in our lives.
Steve