Strength is not tested or demonstrated during times of ease. Rather, it is during times of adversity that one finds out just how strong he is.
Man is not promised an endless supply of strength for him to store up. Rather, God promises to provide the necessary grace and strength for the present trials.
Throughout history, various motives have moved men to sing unto the Lord. Some men sang as a testimony of some specific thing God had done for them (Exodus 15:1; Psalm 126:1-2). Others sang in order to teach truths set forth in the word of God (Colossians 3:16; Psalm 101:1). Some even sang songs that would testify against them in times of disobedience (Deuteronomy 31:19). Though some things have changed throughout history, God’s people still should sing songs of personal testimony like My Jesus, I Love Thee; songs that teach like Holy and Reverend Is the Name; and songs that witness against disobedience like He Was Not Willing.