From Byron Katie

"Sadness is always a sign that you're believing a stressful thought that isn't true for you. It's a constriction, and it feels bad. Conventional wisdom says differently, but the truth is that sadness isn't rational, it isn't a natural response, and it can't ever help you. It just indicates the loss of reality, the loss of the awareness of love. Sadness is the war with what is. It's a tantrum. You can experience it only when you're arguing with God. When the mind is clear, there isn't any sadness. There can't be." A Thousand Names For Joy