The writer of this song is about to get stubborn in his sadness, but first he pours out his soul to God. It's the right approach for all of us when locked in a battle with sadness or depression or even just feeling down. You can't make the best use of your sadness if you can't tell yourself the truth about it.
"Why isn't your God doing anything good to help you?" That's what is implied by the taunts of the unbelievers in the writer's life. They noticed his sadness and challenged his faith in God.
But the songwriter refuses to give in completely to despair; he refuses to give up on God even though he is overwhelmed by loneliness and sorrow. He makes a stubborn choice to remember a happy moment of being caught up in the worship of God (probably at the temple in Jerusalem).
That choice of what to dwell on with his mind seems to lead to the determination we'll see in the next verse tomorrow.
Think: What do you choose to dwell on when you're sad? Have you noticed that choosing to think about happier moments and worshipping God helps you to keep from giving up completely?
Pray: Ask God to help you when you're feeling sad or overwhelmed or depressed to have the self-control to dwell on worshipping Him and on some joyful moments He has given to you.
Do: Write a quick two or three sentences about one of your most joyful memories that included worshipping God.