You then, my child, be strengthened by the grace that is in Christ Jesus (2 Timothy 2:1). With these words, the Apostle Paul challenges his young protégé, Timothy, not to grow weary or weak as he endures for the sake of the gospel and the church in Ephesus. The church at this time was experiencing heavy persecution from the Ephesian culture around it, which had little interest in the gospel. But the church was also facing pressure from inside in the form of false teachers. The church, and Timothy, was pressed on all sides.
Why are you cast down, O my soul, and why are you in turmoil within me? Hope in God; for I shall again praise him, my salvation (Psalm 42:5). Notice that this call to worship comes from David, to David. It is David confronting his own doubting, discouraged heart with the truth of who God is.