As stated elsewhere, I believe God is sovereign (and His will is served) over sickness and disease, and He also loves to heal.
However, some have raised the following concern:
Objection: If you believe it’s God’s will that people are sick, then aren’t you guilty of resisting God’s will by visiting a doctor?
A good athletic coach will work his team hard, causing (temporary) physical stress and pain on the athletes. A good teacher will work her students hard, causing (temporary) struggle and distress on the students. Good parents will give (temporary) consequences that hurt children so that the child grows in character. As the athlete grows stronger, as the student grows smarter, and as the child matures in their character, they will, in some ways, overcome the pain caused by their coach/teacher/parent, which will very much please the coach/teacher/parent. In the same way, God strengthens us through sickness, and part of that strength comes from working to bring healing (on yourself or others) – which can very much please Him.
Let the beautiful God-ordained process of metamorphosis be our guide. During this transformation, the caterpillar is in tremendous pressure and anguish. However, if the chrysalis were to be cut open prematurely, though the caterpillar’s struggle would complete, it would never grow strength to fly as a butterfly. It is only when the caterpillar has struggled completely that it builds enough strength to break open the chrysalis on its own. And it is this struggle that gives it strength to fly as a butterfly. If the caterpillar would have said, “Well, God gave me the chrysalis, I should just relax,” it would never fly. Or if others would cut the chrysalis prematurely it would never fly. Instead, God wanted it to struggle to learn how to fly. God gave the trying circumstance in order to provide a way for the caterpillar to fly. In the same way, He delights when we seek healing (in fact, it is very much in the DNA of every sick person to want to be healed!). But this does not mean He did not bring the sickness for us to struggle against.
Even Jesus Himself, knowing that crucifixion was God’s good and perfect plan, can still say, “Father, if you are willing, remove this cup from me. Nevertheless, not my will, but yours, be done,” (Luke 22:42). As a Man, He is saying, “This is tough. If it can pass, please let it pass. But if it can’t, then let Me endure it well.” In a similar way, we can pray and struggle against our own sickness, not knowing how temporary (and all sickness is temporary in comparison to eternity) it will be, but contenting ourselves on God’s ways over our own ways.
For a related subject, see Is God Sovereign Over Satan?