I don’t have any scientific studies to back up this opinion but I’m going to stand by it anyway:
An ability to make good decisions is the single biggest predictor of long-term success.
There are two operative words in that prediction: 1) good and 2) decisions. Both of these seem like relatively straightforward words with simple definitions. But as with so many things in life, making good decisions is neither straightforward nor simple.
The biggest problem with good decisions is understanding where the judgment of a decision being “good” comes from. Plenty of decisions that I thought were good (even after the fact) were not considered good by others. Doing “right” is often the opposite of making “good decisions.” This is because most of our long-term success will be impacted by how others evaluate our performance. Even if you go into business for yourself, your employees and customers will be evaluating you.
Decisions are everything from the little to the large. Even the decisions you make around what time you start and end your day come into it. In many places, an early start/late end is a good decisions but some organizational cultures weigh work/life balance much more signficantly. Not making waves with coworkers may seem like a good decision but some may look for direct conversations as an indicator of success. Similarly, creativity and independence in decision making is sometimes valued but certainly not always.
Parameters for being successful change moment to moment and situation to situation. You can be in the exact same situation two days in a row and the “good decision” is polar opposite simply due to timing. Often, the ability to navigate these shifting waters is judgment. If you can quickly evaluate and understand the nuanced way that decisions are evaluated you will be positioned to do well.