Horatio is uniquely impassive throughout the story, and although Hamlet admires him and praises him for his dignity, he fails to follow his example.
Why is Horatio unable to reign Hamlet in and protect him from his misguided impulses?
Because Horatio makes no effort to influence Hamlet and allows Hamlet to proceed with abandon, revealing himself to be an insincere and untrue friend.
Because Hamlet changes his mind about Horatio, deciding that he is insipid and uninspiring, and that his dispassion makes him a boring person.
Because Hamlet is convinced that he must pursue his course of revenge, and although he admires Horatio, he views his own circumstances as unique and sees Horatio’s qualities as inapplicable to his own situation.
Because Horatio is an unassuming individual who respects his friend and would not presume to advise him on matters he has not personally experienced.
Because Hamlet’s words to Horatio are false praise; he speaks them to Horatio only to prevent his own loneliness and he does not sincerely believe them.