Joy should overcome Sadness!
(From a sermon preached in 1522 on Philippians 4:4-7)
The repetition strengthens the apostle's exhortation, and I dare say this is necessary. For since we are living in the midst of sins and evils, both of which drive us to sadness, the apostle wants us to rise against them; and although we at times fall into sin, yet we should let our joy in God be stronger than our sadness in sin. it is, of course, true that sin naturally brings sadness and trembling of conscience in its train and that we cannot always be without sin, but yet we should let joy rule and christ be greater than our sin, as John says...(I John 3:20): "If our heart condemn us, God is greater than our heart."
(What Luther Says - p. 692 - para 2148)