I would guess that there has never been a culture which struggled so much with the question of personal identity as ours does. We have invented a whole new period of life - adolescence - devoted to working out who we are. We are constantly being encouraged to be true to ourselves, without a strong sense of who/what we ourselves are, beyond our instincts and most basic desires. Our society is so unstructured that many of us spend most of our lives trying to work out what we should be doing, and then usually end up doing something different. My suspicion is that this is just as true in the church as it is outside it.
My guess is that this is at least partly a hangover from substance dualism. In substance dualism, a human being is divisible into body and soul, with the latter usually being regarded as the real 'you' and the former being basically a vehicle to which you are in some way attached. (The Biblical view of soul/body is rather different, as is now generally acknowledged. However, dualism ruled in Christian thought for most of Christian history. Unfortunate.) One of the many problems raised by substance dualism is that it locates my real identity in something which is basically amorphous and pretty hard to pin down. Where and what is my soul? How can I know myself if I am basically a substance to which neither I nor anyone else has real access? This problem develops through Hume (there is no soul; what I call myself is just a stream of perceptions which are in some sense tied together) and Kant (we are to understand the 'I' as a transcendental, and therefore inaccessible, object of pure reason, the postulation of which allows us to tie our experiences together) into the present uncertainty. We are left grasping for the 'real' us.
Two theological reflections:
Firstly, I don't know myself inside out, and searching within me for my identity is always going to be problematic. I find myself in my relationships with others, who often see things in me that I don't see. Ultimately, I find myself in knowing God, who knows me perfectly and sees everything there is to see in me. When he reveals himself in Christ, and through the death and resurrection and the outpouring of the Spirit reveals me in Christ, I should be content that this is who I really am. Relax: you're identity is not yours to find or make. Yes, it is to some extent hidden, but it is hidden with Christ, and that is a good and safe thing.
Secondly, you and I have not finished living yet. Who we really are is pretty hard to discern amongst the diverse strands, the various stops and starts, the failed projects and the projected dreams, that make up our lives. It is really only after death that my identity can be written, and even then only from a limited perspective. But God knows every day of my life before a single one takes place. He knows who I will be. Relax: this stuff is in safe hands. Stop fretting about what you should be doing, and do what you find in front of you to do, to God's glory.