You bring your uniqueness to the table every day. You don't have to define it; you don't have to know how you're different than anyone else. You can just assure yourself that, simply by being here, you meet the criteria. To be wondering constantly why and what for and how is to trap yourself in a bubble of distorted self-reflection when you could be spending that limited energy elsewhere.
Just assume your right to be here and take comfort in the fact that someone, somewhere thought you were the perfect match to this incarnation. There is power and freedom in that belief, that belonging.