Musar על ברכות 20:11

Likewise Chizkiyahu said: "to peace it is bitterness for me" (Isaiah 38:17) since the Holy One, blessed be He, answered him: "I will defend this city to save it, for My sake and for the sake of My servant David" (Isaiah 37:35). This is as the statement of our sages: "whoever makes his request depend on his own merit, is shown that it was dependent on the merit of others" (Berachot 10b).