We all only have so much time and attention, and with constantly being pulled by work, friends, family in various directions we are only able to give our own causes and ambitions a percentage of ourselves.
Opportunity cost is what we lose out on for taking one path over another. In a way opportunity cost is infinite. We could at any time take any of thousands of possible actions which could, in aggregate, lead to very different futures.
In the present though, opportunity cost is speculative. We can’t know for certain how much taking one action over another will be better or worse than another action. Although we usually have enough information to help make informed choices.
Making the optimal choice is non-trivial. And so we apply tools to help us make smart decisions. We go to school to understand how things work, study history to learn how things have been done in the past, and use frameworks to help guide us to use best practices.
Going against these best practices are countless other factors. Emotional impulses, reaction to external factors, others asking things of you, habits, and restraints. They act like friction preventing us from making better decisions. Some of these things we can easily do things about, recognize and counteract. While other things are very difficult to ignore or fix.