Losing my patience

I'm at that point where I just want to break down and cry, I'm losing my patience with everyone, I'm physically and mentally exhausted and I don't know what to do. I just want a hug right now but I can't even turn to my best friend (long story, we're not fighting but it's complicated). 
What do you usually do to unwind? Unstress? I'm at work right now, I really can't afford to cry or break down.