Tonglen is a form of Tibetan Buddhist meditation in which you visualize taking in another person's pain on the in-breath and sending them any relief you have available on the out-breath. It's doing the opposite of what your instinct is - which is to protect yourself from pain and to keep an pleasure for yourself. I'm sure you can find descriptions of how to do it on the Internet. It can be done in a formal meditation session or on the spot when you hear about someone else's pain.