why stop laughing

I don't know why we become so miserables and full of sadness....
Not everything can be traced to the economic crisis and trouble life
we have,even it we can keeplaughing and happiness inside us I think it is
a psychological rather than economic....

Why we hate to live for the happy moment.....
why we hate the other to live happy moments....
why stop laughing and start crying.....
it is not a matter of dog or funny photo or movie
it just something has changed inside us....