Luna sat down and looked Twilight in the eye.  “Twilight, we wish it could.  Perhaps our sister believes that it is possible to lock one’s problems away, but we believe thou knowst it is not.  Discord and our . . . King Sombra were both able to use mental magic against thee, and we just did as well.  In all three cases, thou wert deceived, at least briefly.  We and our sister hope that if thou knowst how the magic works, thou shalt be able to resist.”