If you want to conceptualize Mara, think of it as a skillful way of addressing your weaknesses. This is helpful because it de-personalizes tendencies which you might otherwise find too difficult to deal with directly.
For example, when I get angry and feel inclined to be sarcastic, I can lecture myself on the need to be nice. But that doesn't always work.
It is much easier to turn my guns toward Mara, and vow to defeat it. Addressing difficult emotions? Hard. I'll probably avoid it. Challenging yourself to beat the hell out of Mara? Also hard, but sure sounds like fun!
I like a good fight, and if Mara wants to fight, then I say bring it on.
This is the value of a good metaphor--it gives you space to rewrite your conditioned reactions.
And now that I've thought about it, maybe I'll actually start doing it.