it's annoying as hell that you're seemingly not allowed to display frustration/displeasure in the physical presence of others (who just happen to be there out of mandation, i.e. coworkers) without getting bothered about it - even when (especially when?) you're not actively cooperating.
if i'm having a grumpy day, then. just let me have a grumpy day. do not ask me about it. do not talk to me. do not pass go and collect dollar two hundred. you don't know me, and probably never really will; i will not tell you. so just... please. do not fucking bother me. i need time and space, and you're only making it worse.