However, there are decisions with wide-reaching consequences, and are either undoable, or painful or time consuming to go back on. What does one do then?
You spend as much time as you can to get as much information as possible before making your decision with your best guesses.
Sometimes you will hit it right on, other times you can modify with little disruption and there will be times when you are just dead wrong and need to scrap everything and start all over. When there is no previous track record for what you are doing so much is pure trial and error.
As you experience having to do complete do overs, hopefully, not more than a couple of times, you get better at knowing sooner when to change direction and cut your losses. And because now there is a track record of what you are doing you have better information to make better decisions.
But if you start in another new industry, you start all over again. But what you bring with you is the experience of knowing when decisions are critical and far reaching and you are better at changing direction quickly to minimize the impact of a wrong decision.
Consciously making no decision is fine. Indecision is bad because as time passes options and choices get eliminated and you are left with no choices.