Certainly, I think it is important to practice self-awareness and self-assessment on a daily basis, but there are no shortage of good ideas on a strong startup team. Every few days someone has a great new idea that could be transformative, and from my experience, you try to question yourselves and your assumptions all the time (hopefully in as brutally honest a way as is necessary, though you sometimes wonder if you are fooling yourselves). Perhaps reality is simply more incremental, though it can look dramatic and transformative after the fact. Every sprint planning meeting and every board meeting is an opportunity for rigorous assessment. You just have to work hard to maintain self-awareness, to see things from a truly unique perspective and make big changes when necessary. Outside advisers certainly help. Otherwise, we are human after all, and it is easy to fool ourselves.
At least that's been my experience as a self-proclaimed "self-aware entrepreneur" ;)