It's not really ! Sometimes when you do not trust the people you are around, then by all means you should be cautious, but remember the key word is is people that "You" are around .Remove yourself before opening if you are not comfortable. When you do open, be sure you have learned from that which have you mistrusting to begin with. It should be only when you are sure of whom you are opening up to.
You have a right to say why you are not giving up , or don't feel like.
That is to anybody. Otherwise It will only be your fault.
So I advise you to use better strategies finding those you hang around with, or are interested in.
By their fruits you shall know them.