Researchers believe that some stress can help to fortify the immune system. For instance, stress can improve how your heart works and protect your body from infection. But on a deeper level, rising to challenges and overcoming them is the essence of life.
As a continuation of the class on "The Different Levels On Which G-d Runs the World", this class is on the different levels of sickness, whether ours or those around us. Just as fast-days are a self-induced weakness, which brings us to analyze our lives, priorities & actions, when God sends a sickness, it's not necessarily a punishment but rather a "wake-up call" to induce soul-searching. Life is comprised of such small incidents, some pleasant & others not, some direct & others less so, to keep us awake that we shouldn't live like robots, but rather utilize our Godly free-will to its utmost extent, keeping our lives meaningful & idealistic. Accordingly, even the "bad" messages are seen by Rav Kook as: The process of gradual good.