Как вы понимаете смысл этой фразы? мини-сочинение
-nature provides a free lunch, but only if we control our appetites ("природа предоставляет бесплатный обед, но только если мы будем управлять своими желаниями")
I think this phrase tells us that we must work hard if we want to eat. All our work isn't unuseful. When we'll have finished some work, we/'' get a prise, at this phrase- food. This note makes this moment clear that our work result will always have a prise. We can also tell this phrase so: "You want to eat? Go and work."