You mature into an adult whether you like it or not.
An emotionally mature person is one who is able to handle his emotions well and is in control of the circumstances s/he is in. He /she makes decisions rationally and takes responsibility for his or her life
He is able to handle criticism or negative happenings well and is resilient.
S/He is well adjusted an within self and with others.
https://hubpages.com/health/Emotional-health-tips-... may help