God is the ultimate encourager in suffering...
Christians should not lose heart even though their bodies will waste away…
Christians should not lose heart because we are being renewed day by day.
Christians should not lose heart because the sufferings of this present time are not worth comparing with the glory that is to be revealed to us ( Romans 8:18 )
In view of the future glory he anticipates inheriting, Paul no longer focuses on the visible, temporary things of the present, that is, the suffering and adversity of the evil age in which he still lives (cf. Rom. 8:24–25). Instead, Paul’s focus is on the unseen things to come, that is, on his growing, Spirit-empowered participation in the image of God, culminating in his final transformation into God’s likeness as manifest in Christ (cf. 3:18; 4:4, 6).
This is Paul’s response to God’s presence in his life. The power of God that sustains Paul in his weakness (4:7–12) causes him to remain confident in his proclamation (4:13) and in his suffering for the sake of others (4:16). All that God has done and is doing through the adversities of his life (4:1–15) leads him to focus on all that God will do (4:16–18), which in turn gives him confidence to endure the daily consequences of sin (4:1–15). This is the cycle of faith.