Sounds like I should be giving you a punchline to answer the title 
I'm quite emotionally repressed controlled, so I've never got to the point where I have to leave off MNing to gather myself in RL, but I can imagine if I got really upset or angry about something on here I might need a break for a while.
So how do you know you've crossed the line where you have to flounce take a MN rest for your good?