"The fact is that attaining or realizing a higher value demands a greater effort of will. So in order to spare ourselves the effort, to excuse our failure to obtain this value, we minimize its significance, deny it the respect which it deserves, even see it as in some way evil, even though objectivity requires us to recognize that it is good. Resentment possesses as you see the distinctive characteristics of the cardinal sin called sloth. St Thomas defines sloth (acedia) as ‘a sadness arising from the fact that the good is difficult’."
John Paul II, Love and Responsibility