Relass your Ass (alike "Relax Your Tits"), is a phrase to tell somebody to be easy and relax when a situation is not at all difficult to achieve. In Mexico, Relax your Ass = Relaja la Raja...
Case # 1.
Dude (sobbing) : Hey bro please help me, tomorrow is the fucking exam and that's my last chance!!!
Friend (badass): Relass your Ass man!... believe me, is less difficult than it looks.
Case # 2 (In Mexico City)
Dude: No inventes, ahí viene mi novia y no me he bañado...
Rascal: Relaja la Raja wey, ahorita la entretengo :)
Theory that a perfect ass has three attributes:
1. Lower butt - The lowest part of the ass, should be firm but not hard.
2. Middle-earth - Middle of ass, should be softer than the lower butt and stick out more.
3. Heaven - Highest part of the ass. "As above down below". Should be similar to lower butt.