Seeing other people happy, either adults or children, always gives me great joy.
Driving early in the morning on a terse spring day when light and shade play in the fields and in the trees and the air seems to sparkle like a crystal in the sun gives me joy. Seeing people succeed against all odds gives me joy. The intuition of God's goodness fills me with joy to the brim. I guess I must be a joyful person :-)