The first and largest complication of writing about identity is its definition. When you write about a subject, you need to define what is included and what is not included. There are certain aspects of your personality that you may feel are central to who you are, but other parts may have nothing to do with it. For example, you have to think about whether your actions are part of your identity. These actions could be anything from hobbies to achievements, and you'll find that some of these actions shape you, while others are irrelevant. When writing about your identity, you'll only want to include those actions and aspects of your personality that have truly shaped who you are.
Another obstacle to writing about your identity is your ability to be introspective. If you are unable to be introspective, then you may find the depth of your identity lacking. This will come out in your writing, and you could be perceived as superficial or two-dimensional.
Although you may have your own definition of what makes you who you are, others may disagree. These outside influences may be anyone from your family, peers or friends to the community as a whole. You must take all of these influences into account when you are writing about identity, as they may have helped shape who you are.
Outside influences can also shed a different light on your identity. For instance, a man accused a murder knows that the community thinks he is a murderer, even if he is innocent. This dynamic will become part of the man's identity over time.
Your own memory also can play a part in complicating your ability to write about your identity. If your memory falters, then how you identify yourself may not match reality. Also, your perception of a memory could affect your identity. For instance, if you remember being persecuted, but in reality perhaps you weren't, it would affect your identity.
Even if you have everything else in check, your own writing ability could undermine the process of writing about your identity. Your writing must be concise and interesting, and it must flow. You cannot float from one topic to another; your writing must lead in a steady direction.