Happiness is a momentary jubilant feeling of a happenstance. It’s physical in nature, fleshly. Joy is an everlasting victorious life that indwells the believer in Jesus Christ. It’s spiritual in nature.
Happiness is but a leaf on the branch of life, but Joy rests at the root of the tree of life.
Joy comes by embracing the liberty that’s in Christ; happiness comes by the performing of righteous works of the law.
Joy is everlasting, while happiness is fleeting.
The joyous life in Christ is predicated upon the belief on His finished work on the cross.
Joy: one of the nine fruit of the “fruit of the Spirit” on the tree to everlasting life.
Galatians 5: 22-23: But the fruit of the Spirit is love, JOY, peace, longsuffering, kindness, goodness, faithfulness, gentleness, self-control. Against such there is no law.