HaRav Yeruchom Levovitz zt"l
Chazal say: "One should always pray not to become ill, because if he sickens he is told: produce merit — show that you are worthy of being healed.
This is perplexing: does one only need merit when he is ill and not when he is healthy?
The Mashgiach HaRav Yeruchom established an important rule: A person should pray that he not become ill because if he does sicken, he requires a miracle and disturbs Hashem, as it were. He surely needs merit if he is well, the difference being whether he is considered as an individual or part of the community.
He brings an example: HaRav Yisroel Salanter said that this world is likened to an expensive hotel. A person is able to pay for one meal through all of his accumulated merits.
HaRav Yeruchom expanded and said that a hotel has rooms occupied by several people where the fare is cheaper. A private room is much more expensive.
The conduct of the world vis-a-vis the public is general. The sun shines for everyone, as does the moon. A person should pray not to get sick because while he is well he is included with the general community and his merits suffice to keep him well.
But if he becomes sick, he requires individual help, a miracle, a private suite. And then he is told: you have to [pay for this and] produce merits because special attention is expensive. If he does not have with what to pay, he may not deserve the healing.
"From here we learn how important it is for a person to follow the general, natural path of self protection, to be part of the community and not set himself apart where he might have to resort to a miracle for his recuperation. It is not difficult for one to be part of a large representation where he does not have to stand alone, on his own merits."