Not true. You can be really honest to your beliefs and have a miserable life specifically because of that.

I have deleted by FB account twice and then I was spending lots of time explaining why, getting weird looks from people and being left out of comments (e.g. people would post something to FB and be laughing about it later but never explain about what.. really impolite of them but what can I do? engage in more arguments).

So yeah, be honest to your beliefs, just don't expect that will translate to happiness (unless you really work on telling yourself none of that unpleasant situations are really bad). We are human beings, how we interact with others matter (even if I didn't want any of that).