Choose to be happy always and avoid being sad, because a happy man always have a beautiful face and think positively, doing that gives you a good relationship with people living around you. Because they always see your smiling face and not the other way round.
As long as this life is concerned, there'll always be things that'll make someone feel sad and unhappy, so it's left for everyone to choose how to react to those situations as well as how to handle them.
You can choose to let your problems frustrate you and lead you to depression or you can pretend to not even see them and they'll have less impact on you, let alone make you feel devastated.
It's important to know that problems will always be there, even when you solve them, another one will just erupte from nowhere, so it's essential to always stay positive and know that problems won't last forever.