Before your question can be answered, I think it would be prudent to define what you think is the life you are "supposed to" live. Wouldn't that be the life defined by your upbringing and your formative environment, based on the ideals, values, and morals of those who influence your life?
For many people, the life they think they are supposed to live is one that is comfortable to them, regardless of whether or not they think they are destined for bigger or better things. And many people are terrified to step out of their comfort zone and take a leap into a great unknown, which prevents them from truly knowing who they are and being who they can be.
Also, what is an "authentic" life? A life that is free of social and moral constraints, unfettered by the tedious ties of the status quo? A life where you do what you want when you want, and damn the consequences?
As for me, I'm living neither an authentic life or the life I'm supposed to live. I'm stuck in some sort of existential limbo where the things I want to do are restricted and the things I can do are cut off due to external circumstances, thus leaving me where I have little option other than to just through each day in one piece, good or bad.