"Rejoice in the Lord alway: and again I say, Rejoice." (Philippians 4:4)
In "God's Word for Today", David Woods writes:

We understand the joy that God gives the Christian is not a surface emotion like happiness. Still, to instruct the Christian to rejoice “alway,” in every situation, might seem unrealistic. As Paul wrote this, do you think he recognized how many might see this instruction as a bit unrealistic?

Teachers, how should you plan to answer students who might see this instruction as unrealistic?
Source: Biblical Family Values, Adult Teacher's Insights, page 76.