Despite weariness and his desire for a peaceful life, Hiro knows that he has a fulfilling existence and this knowledge keeps from a depression funk.
Hiro reminds his teammates that he can't do everthing himself and regularly thanks them for their help. This, in addition to doing a part themselves, keeps them from feeling useless.
Played For Drama: As a result of Hiro's fight against the darkness, his fight inexorably exposes him to the inherent suffering, death, and tragedy in the world. As a result, it takes its toll on Hiro's psyche, altering his personality (though his core morality is unaffected). These changes turn him into a Hurting Hero, Shell-Shocked Veteran, Good Is Not Nice shadow of his original self. Hiro's love for the world makes him believe that he has to grow apart from it and push people away from him. While he carries a seeming mask of fearlessness, Hiro is always scared because he knows that any misstep could make the next battle his last. After a long struggle against the darkness he chooses a successor to pass his mantle to; someone younger and more idealistic like he used to be.