We feel happy when we remember events that made us happy when they happened. Those events made us happy at the time, and they still make us happy now.
We also feel happy when our future plans are going well. The event hasn’t happened yet, but thinking about it makes us feel happy.
When we feel extremely sad, it is difficult to enjoy those events that used to make us happy. We can remember them, but not for long. It sometimes seems like they happened to someone else!
We feel like we are drowning in our sadness. We occasionally manage to bring our heads above the water, and breathe in some happiness.
For example, someone you really like (e.g. a friend or close relative) tells you that something nice has happened to them. You feel so happy for that person. But the moment soon passes. You either become sad again, or you go back to a place between happiness and sadness. (If you don’t feel happy and you don’t feel sad, what do you feel???)
Anyway, back to your close relative’s good news. You have to keep reminding yourself that the person’s happiness is also your happiness. And you do really feel happy for the person!
However, you are still feeling sad about your own situation.
Let’s take another example. You go to a party and you really enjoy yourself. You feel happy. But after the party finishes, you sink back below the surface! How do we continue to stay happy?