One of the world's most powerful forces is feedback. That applies to people and startups, both.

In an organizational sense, I'd argue that the most powerful force of (organizational) physics is the feedback loop (person-to-person, function-to-function, and most importantly, customer-to-company). At a personal level, however, I'd argue that most people don't do enough to seek feedback. Irrespective, the action that's imperative to success:

Play Live.

Simply put, present your startup and its work to an audience, and get constant feedback. Put your product out there. Put your writing out there (This blog is one such attempt). Put your thinking out there. Get people talking about your work, and get people talking openly about your startup and your work. 

While you do this, there are two things to stay extremely mindful about:

1. Staying Scientific. Assume you're not fully right until proven otherwise. (i.e. if someone presents a counter viewpoint or says you're totally wrong - stay open to the possibility)
2. Staying agnostic the nature of feedback. Accept the good, the bad and the ugly - and then decide how you use it.

When in doubt, play live to your audience. Feedback will clear up any doubts and improve your thinking, and products.