Not all prayers for healing will be answered in this age. God may withold healing for his own sovereign reasons. Though we continue to experience the ‘sufferings of this present time’, Rom 8:28, and ‘groan inwardly as we wait for…the redemption of our bodies’, Rom 8:18,23, we nevertheless ‘know that in everything God works for good with those who love him, who are called according to his purpose’, Rom 8:28. Paul recognised that ‘our outer nature is wasting away’, 2 Cor 4:16, and that sometimes sickness and disease would not be healed. Whatever his own ‘thorn in the flesh’ was, he learned that God allowed it to remain for a purpose, 2 Cor 12:7-9. Epaphroditus was near to death, and God did not heal him at first, Php 2:27. Paul told Timothy to drink a little wine for sake of his frequent ailments, 1 Tim 5:23. He left Trophimus ill at Miletus, 2 Tim 4:20:1:6-7 4:19 Jas 1:2-4 have words of encouragement for those suffering trials of various kinds.
When God chooses not to heal, it is still right that we ‘give thanks in all circumstances’, 1 Thess 5:18. God can use affliction to draw us closer to himself, Ps 119:67,71.