I think this image makes more then 1000 words. Yes we are seeing the world as we are. Had you seen when you are happy it seems that all people you meet are happy and all the world is yours, you are full off optimistic and enthusiasm
Now think about the moments you are sad and you are feeling disapointed. How is your world? How are the people that you meet? How is you day?
Do you see the difference?
Anyway nobody cares if you are sad or happy. So chose to be happy and you will find happy people!