Second time now..

Am I being too serious?
Should I treat work colleagues as work colleagues only but never as friends?
Should I always keep a distance to protect myself?
But how do I back off? And to what extent?

This is the second time I get hurt by people I work with.
Did I do anything wrong by being nice to people? Can't understand!

Very upset.


P.S. Haven't resigned yet. Boss just found out his dad has cancer. Not a good time now, feel sorry for him.