I annoys me when random people on the street/in shops/on public transport tell you to 'smile' or 'cheer up'. I have had it happen to me twice in the last week! It's not always the case that I'm down, but I'm often deep in thought about something.
Normally it will annoy me for a minute but then I forget about it, but on a bad day I feel like telling them where to go! We don't all walk around like Cheshire cats and what right does a stranger have to tell me what to do. I don't think they realise that they could genuinely upset someone. Not everyone has something to smile about everyday, often it's quite the opposite and its taking all their strength to get up in the morning...so please just be quiet, if anything you're just giving me another reason not to smile.
Rant over phew