I am trying to think of a word, other than mature, that means "to have a lot of life experience" and that would be able to describe a person with such. (By "life experience" I mean more than just growing up and learning to live in the world; more like "to be good at interacting with people and dealing with things negative and positive as if it were a skill.")
For instance the word guile can mean to have sly or cunning intelligence (from a quick google search of "define guile"). So with guile you could say that a person has plenty of guile.
Best Answer
worldly-wise (or world-wise)
or worldly
have been around (a bit) (informal)
a man/woman of the world
Also ripe, seasoned, hardbitten can be used in this context.