Rejoicing is not dependent on emotions but on the promises of God

God is a God of truth. Do not be ruled by fickle feelings and fleeting emotions; be ruled by the eternal truth of God. Seek to understand the truth of God in all things. Seek to understand the purpose and calling of your life according to the truth of God. Seek to understand the movements of God according to the truth of God. Seek to understand the difficulties of this world according to the truth of God. Wherever there is a lack of understanding, ask God to light up your eyes with His eternal truth.

The hope of the gospel is that God has brought salvation to sinners. So when sickness comes, rejoice because God has promised salvation and glorified bodies. When you are frustrated with the struggle over sin, rejoice that God will one day totally defeat sin and death. When the brokenness of this world seems overwhelming, rejoice that God is overcoming this world and establishing His eternal kingdom. God has provided salvation, God is providing salvation, and God will save the elect. Rejoice in the salvation of God.