One example of this is when Hamlet views Fortinbras' army marching towards the frontier and he considers the bravery of these men risking everything for what will likely be only a minimal gain.  He looks at this act of selfless courage and finds resolve in himself to act according to what he thinks is right, to work to avenge his father and spend no more time debating and hemming and hawing.

Another example might be tied to Hamlet's attack on Claudius at the close of the play.  He has finally decided to act on his feelings and the conflict with Claudius and Hamlet's bravery in confronting him lead Hamlet to better understand his own role and to embrace the role as a leader of men and an important part of the state of Denmark.