"What?"

"Nothing. Just that. That's what my wife said."

You don't have to be happy all the time. It's something his wife said once. After he had lost his hat. And then shared that he was no longer happy. She said many things. But these words stuck with him.

Eventually they became not her words. But became a thought he had in his head. Playing over and over again.

You don't have to be happy all the time.

This felt true... when he was thinking in the context of another person. He didn't believe other people had to be happy all the time. Yet when it applied to his own life... it became hard to accept. He couldn't stand not being happy all the time.

If he couldn't be happy all the time, he'd rather be dead he thought.

This is what made his wife force him to see a therapist.

This made him even unhappier. 

Not the therapist part. The part where his wife forced him to see one.