Why I can't control myself ?

i think you needn't force yourself to smile if you don't really want to do that.everyone has the right to smile and to not smile.of course we can not smile when we are experiencing bad things or feel painful,it's nature for all people,I believe. so,my friend,if you have something unhappy,try to forget them,do something which can make yourself feel comfortable and excite.smiling when you feel happy,don't control yourself about that. all the best!