The ability to change
It is very easy to form an image of yourself with the friends you hang out with and start to conform to the will of the herd, It is often a lot more challenging to change who you are around the same people.
It takes a lot of effort to choose people you want to be surrounded by and often you fight hard against others to form the identity you end up with, so in order to then change that image you have to either fight the people you have already fought to be where you are or you end up fighting those who accepted you as a part of the clan.
It is really easy to see this option and realize that you may as well be a cast away so that you can change on a whim and not have to answer to anyone who questions you, or alternatively you are extremely confident in the you that you believe in and you have challenged it sufficiently that no amount of new evidence or thought provoking questions people prod your image with, you are able to defend it. A lot of the time it will take a while to determine what questions need answers and what questions you are happy with the unknown as a valid answer.
The best part of choosing who you are and who you would like to be is hopefully it is an identity that is challenged very harshly and therefore you end up confident in it and able to defend it with reason and logic, because if not this also gives rise to lunacy and cult like behaviour that is misplaced because of a willingness to have far too many unanswered questions.
To know yourself and your beliefs, it is very important to question them and have enough evidence that is substantial and satisfying in most cases