Someone has just unfriended you on your social networking site -you have no idea why.
You're telling someone about something memorable that happened to you when you were little.
You have to give a short presentation in class without using any notes.
You're telling someone a story, but you get distracted.
You're taking a class, but you're not sure you're learning anything.
You're trying to remember the name of the author of a book you've just read.
That really sticks in my mind.
I hope I get something out of this.
It's beyond me why he did that.
Sorry. I lost my train of thought.
I have to learn it by heart.
It's on the tip of my tongue.