Being assertive is important in life. Without putting forward one's values and opinions in an explicit way, nothing changes in the tranquility of the universe. On the other hand, I think it is equally important to be a skeptic, being doubtful of one's own view.
From time to time, I encounter people who are quite positive about what they think and feel. When there isn't an accompanying element of self doubt, I feel a bit strange. I get suffocated even, having the sensation of being driven up against the wall. It is actually those people who are cornering themselves towards dead ends.
By being doubtful of the self, one opens the door for learning and growth. Looking back on my own past, I realize that I have never been completely sure of what I held to be my own opinion. There was always a remnant fluctuation, a vibrating center of the self swayed to and fro by the invisible wind.
I am very proud of my vulnerable nature. Being vulnerable for change is the only way of life.