Face it: everything that passes through your brain is really someone else's identity-froth, collected and passed on until it got stuck there somehow. It means you're not a specific "someone", but really a mix of other people's identities poured by accidents in that particular blob of greasy neurons in your head. You're not even really living yet. You're not someone, yet. You're not, yet.
I don't this as the problem. If true living is defined as being a source of unique or different concepts then we're all fucked and have been for a great while. I would agree (up to a point) that its statistically likely that every possible idea has already passed through the mind of a sentient creature at some point. I'd also find it likely that one individual, given a normal lifespan, could not possibly come close to thinking of each of those ideas on their own, even with a limitless body of data to expose themselves to. Furthermore, for each of those idea that our collective species has thought up, how many have we tried? Of those, how many have succeeded? How many of the failures were done right?
The problem isn't in being defined by others' ideas; its in being defined by others' RESULTS. There were plenty of people who thought of powered flight before that first bicycle-powered glider got airborne, and I've seen enough comical attempts to fly to estimate that, of the limited number who got off their asses and tried, most of those thinkers failed miserably. Its not the people that think of new things that matter, its the ones who are willing to try, and (far more importantly) willing to fail that are really living.
What I'm trying to say is, if you didn't have an epiphany today, don't sweat it. If you didn't have a goal, time to evaluate.