Il bue si stima per le corna, l'uomo per la parola.
An ox is esteemed for his horns, a man for his word.
So there you go, a guy who breaks his promises is like an ox without horns!
Grammatically this proverb is a good way to remember the "impersonal si" (si stima). The impersonal si is what you use when you want to make a sweeping, general, universal statement, without referring to anyone specific. In English we use "one", the generic you, or even we, they or people to get this idea across. E.g., "In Canada they play a lot of hockey." The "they" in this sentence is not referring to anyone specific. You're not pointing to an actual group of people playing hockey. You just mean it in a general way. To get this point across in Italian, you would use the impersonal si. "In Canada, si gioca molto a hockey." To form the impersoanl si you just take any verb in the lui/lei or loro form and put "si" in front of it. Si vede / si vedono: one sees, si parla / si parlano: one speaks, si capisce / si capiscono: one understands. So how do you know whether to use the lui/lei or loro form? If the noun that comes after the verb is singular, you use the lui/lei form, if it's plural, the loro form. A Roma si vede il Colosseo. A Roma si vedono molti turisti. Usually if there's no noun after the verb but an adverb instead, you use the lui/lei form - In Italia si mangia bene. C4N!