Context

The first installment of the Harry Potter series, Harry Potter and the Sorcerer's Stone, finds our hero Harry learning all about his tragic past.

When wise mentor Dumbledore finds Harry once again staring into the mirror of Erised (it's "desire" spelled backwards 'cause it's a mirror... get it?), he lectures Harry on the dangers of the mirror. The mirror shows each looker his or her deepest desire, Dumbledore claims that the happiest man on earth would only see himself in the mirror, exactly as he is. 

Harry definitely doesn't see himself—has come back to the mirror so he can once again be with the family he doesn't remember.

It sounds like a nice way to reconnect with his dead parents, but it's also a dangerous habit. After all, if you can have back the family you lost, you don't have much incentive to go back to your normal life without them.

Where you've heard it

You've probably only heard this from your wise, wizard mentor.

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

"It does not do" isn't how normal people start a sentence. Just saying.