All beings are interconnected. Hence the energy we project out into the world has a natural boomerang effect. Toss a boomerang of anger, and anger is what will come back to you from others. Toss a boomerang of love, and love will be returned. This, in simple words, is how the law of karma works.
From now on, be sure to perform actions that will have a positive impact on the world. If you practice otherwise, you risk harming the world around you and as an extension yourself too.