Change comes in verse 16. Hezekiah acknowledges that by these afflictions men live, and that they have a beneficial influence on man's character. Now God has delivered him form dying, an indication to the king that the Lord has forgiven his sins. Verse 18 reflects the indistinct view of the disembodied state which OT saints had. Now, because he is alive, he can give thanks to the Lord and tell his children of the faithfulness of God. He is determined to Praise Jehovah all the days of his life. (Believer's Bible Commentary)