In Shakespeare's Romeo and Juliet, Romeo's experience with love so far has been his infatuation with Rosaline. Because she does not return his love, he moons around, sad and depressed as if he life were over. Even his words are sappy:
Love is a smoke made with the fume of sighs; / Being purged, a fire sparkling in lovers' eyes; / Being vexed, a sea nourished with lovers' tears; / What is it else? A madness most discreet, / A chocking gall, and a preserving sweet.
Everyone knows Romeo is despondent over his unrequited love and his friends encourage him to move on.
Meeting Juliet, he does just that. When Friar Lawrence asks if he has been with Rosaline, Romeo answers:
With Rosaline, my ghostly father? No. / I have forgot that name, and that names' woe.
Friar Lawrence is amazed to hear of Romeo's new love, as Romeo had gone on for so long about his love for Rosaline.
Perhaps we also see his immaturity in the speed with which he forgets Rosaline to fall deeply in love with Juliet in just one meeting. However, this is where he seems to turn the corner in terms of maturity, for he is committed to life with Juliet or no life at all.
As he prepares to marry Juliet, Romeo tells Friar Lawrence:
But come what sorrow can, / It cannot countervail the exchange of joy / That one short minute gives me in her sight. Do though but close our hands with holy words, / Then love-devouring death do what he dare. / It is enough I may but call her mine.
Romeo's final actions prove his dedication to Juliet: he cannot be dissuaded from loving her; will not turn his back on her after he is banished; and, he would rather die than live without her. These things seem to indicate that he has turned his back on the childishness of infatuation, such as with Rosaline, to fall deeply in love with Juliet.