"Rejoice in the LORD alway: and again I say, Rejoice" (Philippians 4:4).
Barnes' Notes made this comment on this particular verse of Scripture - "The Christian, therefore, may be, and should be, always a happy man." As a Christian, are you always a happy person? Do you continuously rejoice in the character, law, and promises of your God? Does all your joy terminate in Him?
Matthew Henry made this comment on this verse - "If good men have not a continual feast, it is their own fault." In this verse of Scripture, Paul calls all Christians to a lifestyle of joy that emanates from an active choice of their will - regardless if they are confronted with adverse or joyful circumstances or people. With this in mind, are you choosing to have a "continual feast" each and every day? If not, then know that it is your own fault - for God's power is available to do so.
For the world, joy is wrapped up in success, good fortune, and well-being. Joy for the Christian is a deep-down confidence that God is in control of everything for his good and for God's own glory. In order to obtain this joy, the believer must rejoice in the right object. He is not to rejoice in his circumstances but in his Savior. This requires a familiarity with the great truths about God. John MacArthur said it this way - "Knowledge of God is the key to rejoicing." With that said - do you find it easy to rejoice in all things? If you find it difficult, it may be because you have very little knowledge of your God.
"Rejoice in the Lord alway" does call for you to "arrange your mind" (Precept Commentary) By an act of your will, you have to determine to obey God's command. If you take the first step, God will do the rest!