“Dont let others tell you what to do or how to live your life…. ” is a statement i hear and utter quite often..
“Walk in my shoes and only then will you know” is what comes to my mind right after i hear the 1st sentence.. 
But then there is this little voice in my head that says, no the 1st statement is right and you should stick to it, mainly because i believe in it! 
The keys to your happiness lies not with others, but with yourself. Exactly like the door, where unless you give the key or leave it hanging in the keyhole, the person cant enter the room, in life too, we hold the key and should guard it close to our heart!! Happiness is also an Attitude that you need to wear!!
Yes, circumstances and people do influence our lives, but at the end of it all, its OUR choice.. Things might go total opposite direction, we might get beaten down everythime we try something but that doesnt mean we stop living and go about moping and being miserable!! 
We can blame it on things, people, work,life, etc etc, but we know deep down we are the ones responsible for how we feel… 

Am not saying everyone SHOULD be smiling and HAPPY all the time, but heck, give lifea chance and see how it treats you!!
Think about it….