Hi spontaneous sunflower, you make perfect sense by the way.
Through much of your post you've referred to identity (in one way or another). I believe identity comes down to how we identify with both our thoughts/beliefs and our environment. For example, someone with low self-esteem may identify with a challenge in their environment as being highly stressful and almost impossible to overcome, whereas someone with the beliefs which support high self-esteem will identify that same environmental challenge as inviting a form of opportunity for positive growth.
By the way, when I came out of my 15 year battle with depression, most of my beliefs about myself and the world changed. I was a different person altogether (because of how I identified).
I believe, to understand why we think the way we do, we need to travel a little ways back. Most of our beliefs and behaviours are taught to us which is strange when you think about it (many are not our own, they are inherited). I'm sure you can think of certain simple learned behaviours you've adopted, such as responding to a name you've been taught is yours. You would have learned what is 'good' and what is 'bad' in this world. You would also have been taught what makes you a 'valuable' member of society. You know, all this sort of basic stuff. But keep in mind that it's the basic stuff that can trip us up sometimes when it comes to us trying to change our identity because it's so ingrained. Some of this learned behaviour or some of the learned beliefs are things we must unlearn before we can move on. Easier said than done for sure.
Sometimes it pays to investigate where our behaviours and beliefs came from, why we are who we are at this point in our life. This is not a blame game, just a way of identifying how we may have developed our nature. After all, we don't suddenly become the person we see before us, in the mirror. Once we identify the origins, we can come to better know exactly what or should I say who we're working with (that false sense of self).
An unusual exercise yet one that can be quite humorous involves thinking about the behaviours and beliefs you possess. Who did you learn them from? I bet very few if any of your beliefs and behaviours are actually yours.
I am mum to a 13yo boy and 16yo girl and I regard these people as 2 of my greatest most encouraging and inspiring teachers in life, for they help me unlearn many of my false beliefs as I continue to evolve into who I wish to be.