An exercise for the day:

Stop being so fucking negative.

Stop it. Just for one day, quit the bitching, quit the whining, quit judging other people and just live your life. See someone’s Facebook or Tumblr update and have a smart-ass comment run through your head? Try not posting it, for once. Smile at people in the street. Tell your friends you love them. Face time with your parents instead of calling them so you can smile at them and they’ll see how happy you are to be chatting with them. Don’t fill your body up with processed foods and energy drinks. Only talk to the people who make you happy.

On a more simple level though - 
If someone says something you think is wrong, don’t bother getting into an argument with them about it. Realise that difference of opinion makes the world turn, realise that not every battle is yours to fight, and move on.
Similarly, if someone says something nasty, condescending or offensive to you, don’t bother yourself to continue their negativity, just respond as quickly and calmly as you can and remove yourself from the situation. Don’t dwell in the drama and anger of others.

Just for 24 hours, and see how much better you feel.