You are what you do
Yep you heard it right. I think that includes what you eat. But my point is the "you" people end up seeing is not the "you" you think you are. It's closer to what you do and what gets seen.
People become their jobs not because it's the evil corporate plan, or that adults are just boring and care about money, or "Life is unfair and soul-sucking in it's nature". But rather because most people start addressing them by their job title, since most of their time is spent being known as a doctor, engineer, etc. (what they do, not what they are)
And right there the answer to the question in the song - "Bulla ki jaana me kaun" (even I don't know who I am) becomes clear - you are what you do.
Similarly, I will end up being what I'll end up doing.
PS: This was written while travelling in Delhi Metro, I would advise against taking this seriously :P