Chi si corica coi bambini si alza pisciato.
If you sleep with kids you get up pissed on.
This proverb warns against spending too much time with people younger or less mature than you. Less literally it can mean not to spend time with people on a lower rung than you in other ways (economically, intellectually, etc).
Grammatically it's a good reminder of the reflexive verbs, verbs where one and the same person both does and receives the action of the verb. We see this in "si alza" (gets up), which is the lui form of the reflexive verb "alzarsi". Reflexive verbs always go with a reflexive pronoun - mi, ti, si, ci, vi, si. Io mi alzo (I get up), tu ti alzi (you get up), lui si alza (he gets up), etc. C4N!