What are some quotes in Romeo and Juliet that show Romeo's growing maturity?

As a character, Romeo matures throughout the play in terms of finally accepting responsibility for his own actions.

Throughout the play, Romeo makes many rash decisions that lead to deadly consequences. Moments after killing Tybalt in Act III, Scene 1, Romeo shows his immaturity by blaming Juliet, who wasn't even there, for killing Tybalt. On page 46, he says,

O sweet Juliet,

Thy beauty hath made me effeminate,

And in my temper soften'd valour's steel!

In other words, Romeo claims Juliet's beauty turned him more feminine and caused him to react on his feelings instead of use his head. By the end of the play, though, Romeo not only apologizes to Tybalt for taking his life, but also recognizes him as his own family. On page 86, Romeo says,

Tybalt, liest thou there in thy bloody sheet?

O, what more favour can I do to thee

Than with that hand that cut thy youth in twain

To sunder his that was thine enemy?

Forgive me, cousin!

Romeo accepts responsibility for killing Tybalt by referring to "that hand"—his own. He asks Tybalt for forgiveness and refers to him as his cousin. Romeo refers to Tybalt as his family because of his marriage to Juliet, and it also shows Romeo is burying the feud and accepting his role as part of the problem.

***Please note that the page numbers correspond to the Dover Thrift Editions of Romeo and Juliet.***