Interesting explanation for something we have all experienced:
Imagine that you have a flight at 8:00 in the morning. Which would be worse, arriving at the gate, breathless, at 8:02, just after they’ve closed the door, or at 10:00, thanks to a couple unplanned delays in your morning. Obviously, the first scenario would cause far more misery, but why? Either way you’re stuck at the airport until the next flight, eating the same bad, overpriced food, missing whatever you were supposed to do after your planned arrival, whether that’s meetings or a stroll on the beach.
The difference between the two scenarios is the intensity of the regret you would feel—a great amount in the former and a lot less in the latter. As it turns out our happiness frequently depends not on where we are at the moment, but how easily we perceive we might be elsewhere, or in another, better situation. With the missed flight, you’re in the airport either way, but when it’s a close call, you can think of a dozen little things that would have changed the situation, and each one brings a pang of regret. So, the closer we are to this other possibility, what we refer to as counterfactual, the unhappier we become.