Happiness

What does it mean to be happy???
Happiness is a mental or emotional state of well-being. 
I was recently told that others do NOT effect my happiness.  I ask myself how can that be.  Yes maybe ultimately my happiness is up to me but can't others alter that?  Living in a state of negativity can eventually catch up with someone.  Just because things may appear perfect, nice house, cars, clean and well behaved children, a happy looking family on a Christmas card is that all it really takes?  I ask myself that daily.
I walk into a perfectly clean and neat pre-school 3 days a week where beautiful women come to pick up their perfect children.  Are they really as perfect as they appear?  Are they hiding something?  They always seem to be smiling.  What would people say if one day they walked in disheveled and clearly distressed?  Would people think less of her, or think she doesn't have it together.  Is it somehow her fault?
In today's day an age we hide behind social media only sharing the good stuff and never share the negative.  Why is this? What are we all fearing?  Maybe that someone may know that were not in a constant state of happiness.  Is it a negative thing to not always feel happy???
I think others do effect my happiness i just have to learn how to control how much they effect it.