Life never seems to be that straightforward. My strengths and weaknesses are not things about myself that I can easily point to or identify in myself. I know that I have propensities toward certain actions, but whether these actions would be judged as being strengths or weaknesses seems to be determined relatively by how you judge actions on a moral basis.
A persons strengths and weaknesses fluctuate and are dependent upon the contextual features of their life circumstances. For example, the strength to hold steady to your values and principles seems to be mostly a dynamic quality of a person, and under certain circumstances they may act against there stated principles.
I guess my point is that a person's 'strengths and weaknesses' are very particular to circumstances, and as circumstances shift and change, our strengths and weaknesses also shift, depending on the demands of the circumstances we find ourselves in.
As for being at peace with myself, well I suppose it depends on how we understand that phrase. I am comfortable with the kind of person I perceive or believe myself to be, but I also want to better myself, improve, grow. Consequently I cannot think of myself as at peace with myself, because I am not fully contented with aspects of myself, or put another way, I always feel I can grow and change.
So I do accept much of life for what it is, but I also have a vision of life, at least on a personal level, that I want to fulfil.
When I was younger, I felt that I had to know what I wanted and what life was about, and I was struggling to understand where it is exactly that I 'fit in'. I've realised since then however that life does not work that way. People do not know what they want from life, or who they 'really are'. I don't have to know either, I can just do my best with whatever it is I am doing, and through that I will find my strengths and weaknesses, whilst also being at peace with 'myself'.