Notsorted - Imagine I am a "friend" who is a total PITA and not only whinging to you about my life, but blaming everyone else while expecting them to pick up the pieces.
I constantly drop hints and sometimes ask outright if you would take the kids for a few hours/take me shopping/listen to me rant on for an hour at a time on the phone.
You're a kind soul. You want to help. But here's the thing. You get NOTHING back. Vague promises to return the favour which never materialise. A fiver here and there that is never paid back. I take the piss whenever I ask you to look after my kids "for five minutes".
You are starting to get royally fed up of me.
And then you come on here and learn about fogging 
Next day the phone rings. You pick it up without thinking.
"Hi, its me" Oh NO. That's all you need. The PITA toxic joy-sucking black hole that is your "friend". And then you remember, and rally.
"Hello" you say, ignoring the whine in my voice. "How are you?"
Deep breath. "Oh, you wouldn't believe it. I am having the shittest day from hell. DS1 has a dentist appt tomorrow and I dont have time to take him. I dont know what to do"
"That's annoying when that happens" you say. You can hear the indrawn breath at the other end. Why aren't you helping meeeee? It says.
"Annoying? It's doing my head in! If I could just get a breathing space..."
"Or not double book everything" you think, as you begin to tune out.
"Oh I know," you say, "Breathing space, ha tell me about it! Listen got to, literally running out the door. Hope you get something sorted. Bye!"
And there you are. Fogging 101 