For most things that happen in life, we’ll never know the real reason why they happened, if there even was one, so we might as well use the more positive interpretation when we explain things to ourselves.
For example, say I apply for a job but don’t hear back. If I’m an optimist, I’ll assume that it’s nothing personal and I will get a job eventually, whether this one or a different one. In contrast, if I’m a pessimist, I might start freaking out that nobody wants to hire me because I’m fundamentally flawed, I will never get a job, and nothing will ever get any better.
It’s the reverse for positive events. Let’s say I enter a picture I took in a photography contest, and win. If I’m an optimist, I will explain it as being a good photographer and having a lot of success in life overall, whereas if I’m a pessimist, I’m more likely to say it was a fluke, or I just got lucky this time.
It seems pretty obvious that the optimistic approach will lead to more positive feelings. But is it foolish to think that way?
I say no. We never learn the true explanation for most situations in life. Was the cashier rude to you because he looks down on you, or because he’s having a rotten day? Chances are, you’ll never know, but the fact is, people mostly think about themselves and their own issues. If they do something thoughtless, it’s probably just that: thoughtlessness. Even in the rare case that someone is trying to hurt you, it’s because they’re screwed up or suffering in some way—it’s still really not about you. It’s far more likely the cashier was rude because of something in his own life. Furthermore, you will be happier if you assume his bad manners are due to his own issues. That’s two good reasons to assume it has nothing to do with you and move on.
Any time you have a choice, choose to explain good situations to yourself as pervasive and long-term, and bad situations as temporary and isolated. Refuse to take bad things personally. Even if you don’t believe these explanations at first, just assume them for the sake of argument, and see how it works out. I’m betting you’ll like it enough to stick with it.