Its actually pretty easy. Just practice with one person and everything they do see it as something that's actually apart of you. If there angry then a part of you is angry. Once you know that its easy to deepen the experience and you'll know how to do that when the time comes.
A tip: when you see someone angry (whos basically just a projection of yourself) or whatever its much easier to heal it because you can't stay mad at yourself too long. You'll notice your social relationships go off the chart. Just send those people, which are you, good feelings and you'll notice they change. Its almost scary at first lol