How does one avoid getting cancer?
Every day one should do what the Gemara says: לעולם יבקש אדם רחמים שלא יחלה– “A person should always plead for mercy from Hashem that he shouldn’t get sick” (Shabbos 32a). Which means that every day you should pray for good health. I know you won’t do it, but listen to me anyhow.
Every single day of your life! Don’t rely on shemonah esrei – you don’t even think what you’re saying. It can be done outside of shemonah esrei, or if you wish, you can add it when you finish shemonah esrei, before you take three steps back. Beg Hakodosh Boruch Hu! Although you’ve prayed all your prayers by rote, by stereotype, like a record; but when you’ve finished, at least one little thing say with kavanah.
Say, רבונו של עולם יהי רצון מלפניך שתשמור בריאותי ושלומי – “Please guard my health and my well-being.” שלומי means, “Guard me against automobile accidents and other accidents.” You have to always pray to be saved from accidents.
What do people expect, that Hakodosh Boruch Hu is going to protect them for nothing? The reason there are accidents in the world is to be a spur, to incite people to pray. But if you don’t pray, so what can Hakodosh Boruch Hu do? He might have to send an accident, chalilah, to make you aware.
So therefore, לעולם, always! לעולם יבקש אדם רחמים– a man should always seek mercy from Hashem, שלא יחלה, not to be sick. And that’s one of the most important pieces of counsel you will ever hear.