Again, bad attitudes are contagious.  If the people closest to us, including family, friends, and coworkers, have negative attitudes, you may "catch" one as well.

Just remember, you don't have to get upset if someone is trying to make you upset.  You can choose to stay happy and upbeat.  I like to think of this as wearing a bulletproof vest.  People can fire negativity at me all they want.  But if you remember that it is their issue, not yours, it should bounce right off you.

- Tabatha Coffey, Own It!

While this tip from Tabatha Coffey definitely falls into the category of "easier said than done," with practice, she is most certainly right.  It is possible to not let someone else's bad mode become your bad mood, and the trick lies in (A) realizing that their negativity is their problem, and (B) staying curious about why they might be acting with a poor attitude in the first place.  This curiosity also helps keep you focused and less likely to react with negative emotions.  These steps mean that you aren't ignoring what is happening to those around you, but instead are trying to understand it without being sucked into it yourself.