He who made you bitter made you wise.

He thought he saw an Elephant, That practised on a fife: He looked again, and found it was A letter from his wife. 'At length I realise,' he said, 'The bitterness of Life!'

there is, after all, no harsher bitterness than that of a person who is his own worst enemy.

It seemed a blinding moment of self-understanding. Hate had been the trademark of his presidency. But in the end he had come to realize that hate was the poison, the engine that had destroyed him.

"You're a bitter man," said Candide. "That's because I've lived," said Martin.

A sight to touch e’en hatred’s self with pity.

Some of my most neurotically fierce bitterness is the result of realizing how untrue people have become.

The bitterest tragic element in life to be derived from an intellectual source is the belief in a brute Fate or Destiny.

"The passion for revenge should never blind you to the pragmatics of the situation. There are some people who are so blighted by their past, so warped by experience and the pull of that silken cord, that they never free themselves of the shadows that live in the time machine...

And if there is a kind thought due them, it may be found contained in the words of the late Gerald Kersh, who wrote:"... there are men whom one hates until a certain moment when one sees, through a chink in their armour, the writhing of something nailed down and in torment.

Its very memory gives a shape to fear. Death could scarce be more bitter than that place!

“Joe, I’ve learned by bitter experience not to trust statements set off by ‘naturally,’ ‘of course,’ or ‘that goes without saying.’”

...How could anything as delicate as love turn into the harsh accusation of [his] eyes? (book 3 chapter 11)