Remember now - The old covenant promised temporal prosperity to the righteous, including length of days. Hezekiah, conscious of his faithful…

Remember now how I have walked ... —Hezekiah deprecates an untimely death—the punishment of the wicked (…

I do not think this was intended to be a self-righteous prayer, though it reads like one, or else the Lord would not have heard it.

He meant…

In these days was Hezekiah sick unto death,.... Of this sickness of Hezekiah, the message of the prophet Isaiah to him, and his prayer upon it, See…

Hezekiah was sick to the point of death in the same year that the king of Assyria besieged Jerusalem. Isaiah brought a warning to Hezekiah to prepa…