Often we become extremely relaxed in our everyday lives and that is perfectly okay but it is important to remember respect. Things may not go your way at all times but that is no reason to forget politeness and manners. Both of those things show people that you are considerate and care about others.
It is important to remember courtesy because in the long run it can get you far. People will look at you differently and begin to put you in a positive light. So take the time out of your day to remember that we are all human and it feels good to have someone be nice to you.