Problem with tiredness and stupidity?

I generaly look at life with a philosophical aproach and wander between romantic and existentialist depending on mood and energy level...but maaan that ****'s low these days.Been working 12 hours shifts with 24 hour rest in between.There's this really nice,cheerful etc. girl at the hotel I work as a porter at and I'm not sure she totaly understands my situation.I'm not emo and she's giving me all the signals even escorted her to her crib the other day and both were too tired for a kiss (or maybe dumb@$$ me was tired and she was just anticipating cause boys do the first step and so so).I guess it's normal to feel kinda f**ked up after a 12 hour shift right?Worst part is I go like "I'm actualy not all that talkative" when I'm tired.And a major part of the problem is when I AM tired it shows every way other than physical...with my shaven head and dark clothes I'm a bit affraid it might give the wrong impression. How do I deal with tiredness after work?Or do I simply ask her at diff hours?