One key concept I discovered in life is whenever negativity arouses within you due to an external factors, simply smile within regardless what is happening. I say that to say, that it's most likely beyond your control if it's an external factor. We as human beings always want to control something whether it's other people, life circumstances etc.. the reason to smile when negativity comes your way is that it's simply a reminder that you cannot control outside stimuli. On the other hand what you can control is the way you perceive it I.E; Someone bumps into you on a busy street and you perceive it as maybe they were in a hurry to see their child in hospital or if a bird randomly pooped on your shoulder, you could perceive it as a sign of good luck or even that it's really no issue because you can go into the nearest restaurant and use their toilet to clean it off, then putting it in the washing machine when you get home.
Key Concept: Your Perception Is Your Reality