Need Help for Tattoo Translation

It's been about ten years since I took any Latin, and I've been called upon to provide a translation for a tattoo, so I figured I should bring it to the professionals here before it's made permanent.

The passage needing translation is the famous quote by Nietzsche:

Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird.
Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein.

This is typically rendered in English as:

He who fights with monsters should look to it that he himself does not become a monster.
And when you gaze long into an abyss, the abyss gazes also into you.

Working with my vague recollection of Latin grammar and my old dictionary, I've come up with the following rendering. Please let me know how off the mark it is and suggest away:

Qui pugnat cum monstris ipsa monstrum decendem caveat
Et dum barathrum diu intueris te barathrum intuitque