Paul knows that once begun with Christ, Christ will finish with you, and finish perfectly. He is praying standing on the believer’s completed position in Christ, Colossians 2:9 – 10. That significantly alters one’s prayer life, at least it does mine. Rather than pray for perseverance through suffering, the prayer becomes that one will stand strong in their completed state worthy of the Gospel in order to bring others and glory and honor to Christ.
Sure we still pray for healing, but more than that we pray that the one who is struggling to stand firm in praise and joy in Christ.