I remember once when someone asked me how they could pray for me, and I replied, "I have Parkinson's Disease........ It gets in the way of my ministry...... I need healing." to which he replied, "I can't". He was saying that since he didn't know God's will concerning my health he couldn't pray for my healing in complete faith.
How could healing be wrong to pray for? After all, Scripture tells us: "Whatever you ask in my name, that will I do that the Father may be glorified in the Son" (John 14:13) and "If you ask Me anything in My name, I will do it" (John 14:14)
Scripture also tells us "You ask and do not receive because you ask with wrong motives, so that you may spend it on your pleasures." (James 4:3)
"Is anyone among you suffering? Let him pray." (James 5:13)
I think the Bible is telling us to take the burden of sickness that you bear to Him. You can ask for healing, but understand that He may not heal you right away, and maybe not while you live on this earth. Your priority in prayer must be His will, not yours.
Remember in the garden of Gethsemene, Jesus prayed, "Father, if Thou art willing, remove this cup from me; yet not my will, but thine be done." (Luke 22:42)
The Bible tells us that Jesus - "being in agony He was praying very fervently; and His sweat became like drops of blood, falling down upon the ground" (Luke 22:44)
We should take our concerns to God in prayer ("Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all comprehension, shall guard your hearts and your minds in Christ Jesus." Phillippians 4:6,7)
And our attitude must be the same as Jesus (ready to accept the will of God).
I remember when in one of my lowest moments, I asked God to bring me home - to let me die. I simply couldn't bear the painful existence any more my life had become. He clearly (though not audibly) spoke to me in all tenderness, telling me that He knew I thought I had no purpose any longer, and that I was nothing but a problem to everyone around me. But the truth is that, though you cannot perceive it, you DO have purpose. I have never left you to go through this alone and I never will. I agonize with you in your pain. But can you trust me just a little longer?
God often does things in ways that seem to make no sense to us. It often seems to be the hard way. But listen for His question, "Can you trust me a little longer? I will accomplish my glorious will and I will fulfill your purpose in due time. Can you trust me a little longer?"