I don’t mean to be a downer here, but your startup is already sunk. You have already made the mistake that will sink you, you just don’t know it yet. At Distil, the decision that sunk us and the actual sinking were separated by a year (read about it here).
Almost anything can sink a startup. It’s usually not the big things, like picking the wrong pricing, the wrong market, the wrong product, or the wrong team. It will be something tiny, almost inconsequential at the time, but in hindsight will be the choice that made it all unravel. That other project you were working on at the same time you were starting yours. The employee you let go for alleged sexual harassment. The option price you picked for your employees. The name you picked when still in stealth mode, the one you were never going to use and planned to change.
Every decision in your startup is important. Treat them all as if this will be the one that will sink us.