unity is strength; many hands make light work; united we stand, divided we fall; there is strength in numbers

(idiomatic) you can't judge a book by its cover; clothes don't make the man, the cowl does not make the monk

one swallow does not a summer make

to err is human

there's many a good tune played on an old fiddle

the straw that broke the camel's back

birds of a feather flock together

no one is indispensable; there are plenty of fish in the sea

Synonym of la verità viene sempre a galla / the devil teaches us his tricks but not how to hide them

do unto others as you would have them do unto you