Pleasure and pain, beauty and ugliness, are all false imaginations of the mind. Mind is a false, illusory product. Conceptions of the mind also must, therefore, be false. Pleasure and pain are in the mind only. It is subjective.
Desires are the cause for pleasures.
You can convert pleasure into pain and pain into pleasure by thinking, by Bhavana , by imagination. Many vegetarian students who have gone to England to prosecute their studies have become inveterate meat-eaters. Meat was very repulsive to them when they were in India. Mere sight used to induce vomiting. By simple change in thinking.