When we contemplate our sensations, we are less likely to experience so much suffering. For instance, when someone is nice to you, you may feel happy at the time. If you then worry whether next time they will still be nice to you, you are now suffering. In that case, your nice sensation of happiness disappeared quickly. On the other hand, if someone insults you and you feel resentment, you are just adding more suffering for yourself. If we learn to contemplate our sensations and feelings, we will see them as transient phenomena and suffer less.
From Things Pertaining to Bodhi: The Thirty-seven Aids to Enlightenment by Chan Master Sheng Yen, page 16