Be kind, everyone you meet is fighting a hard battle.
Sometimes we tend to think that only we have problems and everyone should behave well with us.
But we often forget that everyone in this world has problems, and never say to someone that your problem it's nothing compared to my problem. Maybe you are now on level 10 and they are on level 1, remember that once you were on that level too. Even if you are on the same level, again it's not the same, everyone experiences things differently.
So, be a good listener, listen and care for them, and the most important, be kind. Be kind to everyone, not just to the people you care about, because one good word can change someone's day. Little by little, you see the world smile.