You know the 80/20 principle says that 80% of the value comes from 20% of the effort. (Unequal distributions like this are a pattern, not a law – sometimes it is 70/30 or 95/5.)
But which is the 20% that you should do, so you don’t “waste” your effort on the 80%? Which is the critical few that merit your attention in a new-to-you situation? I can almost always spot the critical few in the rear view mirror, but only occasionally looking forward. In new-to-you situations, you must experiment and push forward and apply what you learn. This is the price of adventures and meaningful work.
If you’re in a situation which feels familiar – either through personal experience or you’ve recognized it from the experiences shared by others – you have a better shot at identifying the critical few, and the levers to move. You can avoid that which you know is ineffective, or a side-show. This is the payoff from reflection, study, and applied imagination.