One of the truest definitions of health that continues to prove itself over and over again is that when we get sick, our immune system can work thoroughly and efficiently so that the illness comes to a full resolution. In other words, being healthy does not mean that we never get sick (which would assume that at baseline we have some kind of perfection of physiology, and illness is always a deviation from it). That makes for a clean model, but is a very static view. We are more dynamic beings than that. At important times an illness process can actually open the door for us to transform and rebalance. Small children are particularly good at this. When they get stressed or worn down, they quickly show the world that they don't feel well (adults are not quite so honest, and we can hold out a lot longer with supports like caffeine, deadlines, duty, and yes, the fear of finally letting down…). But sick children do what their bodies need: they slow down, they lose their appetite, get a fever, whine and cling, and discharge what they don't need (with a drippy nose, loose stools, a red rash, etc). That process needs a few days, but usually children swiftly turn the corner and build back to a good appetite and full activity–often better balanced than they were before. So an essential part of health is that our body has the flexibility to loosen and shift and change to a new state as needed.