(giving Ophelia advices about Hamlet, who has been courting her) Try to think of it like that, anyway. When a youth grows into a man, he doesn’t just get bigger in his body—his responsibilities grow too. He may love you now, and may have only the best intentions, but you have to be on your guard. Remember that he belongs to the royal family, and his intentions don’t matter that much—he’s a slave to his family obligations. He can’t simply make personal choices for himself the way common people can, since the whole country depends on what he does. His choice has to agree with what the nation wants. 

(seeing Ophelia after she's been turned to madness) Oh, heat, dry up my brains! Salty tears, burn my eyes! By heaven, I’ll get revenge for your madness! Oh, you springtime rose, dear maiden, kind sister, sweet Ophelia! Is it possible that a young woman’s mind could fade away as easily as an old man’s life? Human nature is refined and thoughtful—person graciously gives a valuable part of herself away to her beloved, as Ophelia has sent off her sanity to her dead father. 

 (talking about Hamlet violently during Ophelia's funeral) Oh, damn three times, damn ten times the evil man whose wicked deed deprived you of your ingenious mind. Hold off burying her until I’ve caught her in my arms once more! (he jumps into the grave) Now pile the dirt onto the living and the dead alike, till you’ve made a mountain higher than Mount Pelion or Mount Olympus!