It is strange,' he said at last. 'I had longed to enter the world of men. Now I see it filled with sorrow, with cruelty and treachery, with those who would destroy all around them.'
'Yet, enter it you must,' Gwydion answered, 'for it is a destiny laid on each of us. True, you have seen these things. But there are equal parts of love and joy.

That is why your sacrifice was all the more difficult. You chose to be a hero not through enchantment but through your own manhood.

What was there to be gained by fighting the most evil wizard who has ever existed?" said Black, with a terrible fury in his face. "Only innocent lives, Peter!"
"You don't understand!" whined Pettigrew. "He would have killed me, Sirius!"
"THEN YOU SHOULD HAVE DIED!" roared Black. "DIED RATHER THAN BETRAY YOUR FRIENDS, AS WE WOULD HAVE DONE FOR YOU!

We forget cruelty and past betrayal, Heedless of where the next bright bolt may fall

We all struggle alone through the ten thousand joys and ten thousand sorrows of our lives.

One must have sorrow to truly appreciate joy.