"I said, In the middle of my days I must depart; I am consigned to the gates of Sheol for the rest of my years. I said, I shall not see the Lord, the Lord in the land of the living; I shall look on man no more among the inhabitants of the world.My dwelling is plucked up and removed from me like a shepherd's tent; like a weaver I have rolled up my life; he cuts me off from the loom; from day to night you bring me to an end; I calmed myself until morning; like a lion he breaks all my bones;from day to night you bring me to an end. Like a swallow or a crane I chirp; I moan like a dove. My eyes are weary with looking upward. O Lord, I am oppressed; be my pledge of safety! What shall I say? For he has spoken to me, and he himself has done it. I walk slowly all my years because of the bitterness of my soul. O Lord, by these things men live, and in all these is the life of my spirit. Oh restore me to health and make me live! Behold, it was for my welfare that I had great bitterness; but in love you have delivered my life from the pit of destruction, for you have cast all my sins behind your back. For Sheol does not thank you; death does not praise you; those who go down to the pit do not hope for your faithfulness. The living, the living, he thanks you, as I do this day; the father makes known to the children your faithfulness. The Lord will save me, and we will play my music on stringed instruments all the days of our lives, at the house of the Lord." ESV
Death is always a fearful thing in the OT--even for believers. For OT believers, death ends in Sheol which is the final destination of the dead, both righteous and wicked. It's not a place of existence but non-existence--as departed spirits and souls. In the OT concept of Sheol, the departed spirits remain contactable but forbidden. The example of Saul calling out Samuel through the witch of Endor is an example (1 Sam 28:4-23). The Greek OT translates Sheol using the Greek word Hades. However, in the NT, Jesus' story of the rich man and Lazaurus (Luke 16:19-31) suggests that there is a great gulf separating the righteous from the wicked in Hades--the place of the righteous was called Abraham's bosom (another term for Paradise in the Talmud).
When Jesus told the thief on the cross that "Today, you will be with me in paradise," he was referring to this temporary resting place of the departed souls. However, other references to Paradise (2 Cor. 12:4; Rev. 2:7) suggests that Paradise is no longer in Hades but in Heaven. According to one explanation, when Jesus died on the Cross, he went down to Hades and brought Paradise (and OT believers) up with him as he ascended to Heaven, where God dwells. This is now the "Holy City" where NT believers join OT believers in Heaven. But it will one day descend out of heaven to the make its final resting place on the new earth: "I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband." (Rev 21:2).
However, Hezekiah had no such revelation of the future destiny of saints. So, he clinged on to this life as everything he had--the end of which means the end of his existence and ability to give praise to God. When we face death in fear and without hope, it gives the devil a stranglehold on us: "Since the children have flesh and blood, he (Jesus) too shared in their humanity so that by his death he might destroy him who holds the power of death—that is, the devil—and free those who all their lives were held in slavery by their fear of death" (Heb 2:14-15). Jesus' resurrection is testimony to us that death is not final--that there is a hope of the bodily resurrection of all who die in Christ.
If we desire healing and health, we do so only in order that we might serve God longer to fulfill His agenda for us on earth, to complete the "good works" which he has prepared beforehand for us to do (Eph 2:10).
Father, we thank You that You still heal the sick and raise the dead--but only in order that we might continue to serve You and fulfill Your agenda for our life. So, teach us to number our days aright, that we may gain a heart of wisdom. Amen.