As you move through the world your actions cause or reduce suffering, and many times you can’t control which result you’ll get. If you live a life where you cause everyone around you nothing but suffering, you’ll eventually get it back on you.
Ironically, if you live a life where you do nothing but reduce everyone’s suffering, you’ll also live a fairly horrible life full of your own misery. The important thing is that Buddhism balances between reducing your own suffering and that of other people, while still understanding that none of this is really permanent or that important so you avoid attachment (but not too much).
via zedshaw.com