What is the essence of ourselves? Our identity?
There are two approaches to this question.
First, we could look at the physical , biological laws that determine the identity of oneself. Since I am not a physician, take this as my perception of how identity changes with time.
There are variations in the variability ( :-) ) of identity among people. Some people have enduring identities that last a lifetime, while others change per month or day, or according to the next person they will meet. I have noticed though, and maybe this is scientifically accurate that as people age, people are more firm, they lose the ability to change their beliefs. Maybe , this is true because the brain of humans changes with age. Also, the formation of our subconscious reactions seem to be determined very early in age, (for example fear of heights). Again, I am not a physician, take this with a grain of salt.
Thus, one could say that we are predetermined to lose our ability to learn new things, to see things from different points of view and to change our personality.
The second approach is to analyze our perception of our identity, and how our and others' perception of our identity affects us.
Having a specific identity is extremely limiting because then, our future self tries to uphold that identity and thus limits his ability to change. Imagine for example that you are very religious, and then one day, you stop believing, would it be easy to transition to a new identity? How would your relations be affected?
Imagine having fame and respect about something. Would you be able to forfeit all that to follow what your heart truly desires or to experiment with new things that are contrary to this.
Now , the other side of this coin is that identity is a good way of gauging what someone will do in the future. Intellectual and physical ability, one's psychological profile is a very good estimate of future behavior.
If someone is kind-hearted, it is expected she will be in the future too. Imagine if we had great variations of behavior, the one day , kind-hearted, the other cruel, this would't be sustainable. We would immediately want to stop any interaction with that person, because we want stability.
Another point is that ones' reputation also attracts similarly minded people, thus it is very helpful.
What should we then do? What should our identity be?
My solution to this. To be able to have strong beliefs while at the same time, to be able to experiment. And to use one's reputation very seldomly, only when necessary to achieve a goal, or for a small core that can never change, because otherwise, reputation can bite you in the a...rm.