I think a major theme in the play is maturity. Throughout the play, Henry has to make choices that are difficult and at odds with who he was as Prince Hal in the Henry IV plays. The famous example of this, of course, is his treatment of his old friend Falstaff. Whereas Prince Hal admired Falstaff for his love of fun and rejection of responsibility, once he becomes King he rejects Falstaff, a break that leads to the knight's death. One of the things that happens to Henry is that he recognizes that Henry the man and Henry the King, are different people. In order to be a good King, Henry learns that he cannot condone irresponsibility, no matter his personal convictions.