Many proverbs have been absorbed into English having been known earlier in other languages.

Many proverbs have been absorbed into English having been known earlier in other languages. The list here is specifically of English proverbs
and the dates given are those when the proverb first appeared in English.
A cat may look at a king
A chain is only as strong as its weakest link
A change is as good as a rest
A dog is a man's best friend
A drowning man will clutch at a straw
A fish always rots from the head down
A fool and his money are soon parted
A friend in need is a friend indeed
A golden key can open any door
A good beginning makes a good ending
A good man is hard to find
A house divided against itself cannot stand
A house is not a home
A journey of a thousand miles begins with a single step
A leopard cannot change its spots
A little knowledge is a dangerous thing
A little learning is a dangerous thing
A little of what you fancy does you good
A man who is his own lawyer has a fool for his client

A change is as good as a rest

A change is as good as a rest

A chain is only as strong as its weakest link

A chain is only as strong as its weakest link

A chain is only as strong as its weakest link" implies that it does not matter how strong a team is, if they have a member that can be exploited in weakness, then they will all fall. That is why we need to "cover all the bases" and not only prioritize a number of things. We need to be stable in all aspects as to not fail easily. In experiments, the data you gather is only as significant as the worst of your findings, since the validity of the experiment relies on all the stats combined. I think that is what your teacher is talking about.

A cat may look at a king- Proverb

A cat may look at a king means every person has his/her own ability an we must not underestimate people.
It's several hundred years old expression . It usually means that even the lowest person (the "cat") has the right to be with upper-class people (the "king").

You can't judge a book by its cover

Let not the sun go down on your wrath

Let not the sun go down on your wrath

Meaning:

Do not hold on to your anger for more than one day.