Ps 126:5- They that sow in tears shall reap in joy.
Happiness is based on something that happened, or that was done to me that gave me a moment of having a good feeling within. For instance, sex outside of marriage will make a man or woman happy for the moment or a while. But when the feeling of happiness is gone, like a substance abuser needing a fix, we will need something else to happen to bring back the feeling of contentment again. So we must conclude that happiness, while it is a wonderful thing to experience, does not endure long enough to keep us whole. It is also situational. Meaning, what made me happy to bounce back from one situation—may not work in another.
Joy is the fruit of the Spirit. While happiness may escape me, joy is not based on what comes from the outside to cause me to smile. The essence of joy is in the believer because happiness is too weak to truly secure us. Joy will erupt when I think about how the Father loved me so much that He gave His only begotten Son for Me, what Jesus did to save my soul, and how the Holy Spirit dwells within to empower me to prosper although it appears that all hell has broken forth in my life! And though my flesh feels bad because I had to deny it of one of its many desires, my sowing to the Spirit will enable me to reap in joy.