It's good to know the really common English proverbs because you hear them come up in conversation all the time. Sometimes people say the entire proverb to give advice to a friend. More often, someone will say just part of a proverb like this:
You know what they say: when the going gets tough...
(Read #5 below to learn the rest of this proverb and what it means.)
Learning proverbs can also help you to understand the way that people in English-speaking cultures think about the world.
Proverbs can also give you good example sentences which you can memorize and use as models for building your own sentences.