Psalm 106:15 says: “So He gave them their request, but sent a wasting disease among them (literally ‘a leanness into their soul’.”
The Psalm describes how Israel had seen God’s work in the Exodus, but “quickly forgot His works” (:13) and then “craved intensely in the wilderness” (:14). They despised the manna that God had provided for them, and asked for meat instead. This verse says that God gave them what they asked for — but it led to devastating results.
THIS is why we should always pray regarding our requests, “If it is Your will.”
We do not want God to do for us what He did for Israel in the wilderness: give us what we ask for — even if it leads to our demise. How many times do we ask amiss, or “with wrong motives so that you may spend it in your pleasures” like James 4:3 says, and if God granted our request it would lead to “a wasting disease” or “a leanness into (our) soul”?
Let us recognize that despite much false teaching to the contrary, prayer is not for the purpose of giving us “whatever we want” — especially when “whatever we want” comes from a selfish, avaricious human heart! Thank God that He does not grant every one of our requests — there are many which are best unanswered! Rather than insisting that God answer our every request, a better prayer would be that God might give us desires which are according to His heart, and that He would teach us how to ask according to His will in the first place!