dont be afraid to tell people how you are feeling and you dont have to be positive for the sake of others - be true to how you feel.
FG
Best advice I have ever got is to be upfront. Don't be afraid to tell others what you're feeling, or what you need. Even my boss suggested that I say to people "Actually, that's not helping."
Better still, someone told me to say "that's an interesting comment. What makes you say that?" Because it makes them actually consider why they are spouting empty cliches, without you sounding like a biatch.
I ended up hiding under ym desk having a good solid cry a couple of weeks ago, and the more I thought about anyone seeing me cry, the more I cried. But then I went out, and faced them. Everyone. I just said "I'm leaving for the day, I'll see you tomorrow." and they'd all have been able to see that I was upset. It was SUCH a relief because it meant I wasn't acting anymore; I could just live, and be me. I haven't cried since, but I know that I could and it wouldn't be a big deal.

it shows that you're an awesome person, caring enough about their feelings as to take that burden upon yourself. But there comes a time to draw the line, enough is enough, cut the act if you have to. If they can't handle it, that's their problem. (but they'll probably surprise you and you'll find that it's not so bad.)