Life is not an elevator. It is stairs all the way, and sometimes you go up a few and then back one or two. It’s one of the things we humans all have in common. You may think you can name people who are so happy they’re floating in the clouds, but, trust me here, even they get stuck in the rain every now and then. Here are some reasons why it’s OK when a little unhappiness darkens your day. 1. Happiness is never constant. And that’s not so bad. If we don’t have a little sadness or upset come our way, we’d never know what true happiness really is. Even so, many people get angry when they’re unha…