I think shifts can be very draining. I had the luxury of
working almost all evening shifts recently, so things weren't so
bad.
But being in the ICU, whilst a dream come true, has made me
realise that my good shifts are about to end. I just realised
that the 12-hour rosters can be quite crap. One of my
colleagues worked a 12-hr shift (7am to 7pm) on Tuesday, only to
return on Wednesday to work the reverse 12-hour shift (7pm to
7am)!! 
And a lot of 12-hr shifters work three straight days, which I
don't know how they manage, because after the first 12-hour shift,
your body is already very tired, especially if there had been a lot
of changes in the ICU.
I did a late 8-hr shift, followed by what was supposed to be an
early-morning 8-hr shift which ended up being a 12-hour shift, and
by the end of that shift, I couldn't think straight. Went
straight home, wanted to just crash into bed, but had to force
myself to stay awake for dinner cause it's another morning shift
the next day. 
Don't even mention studying... What
studying?!!
Your shift sounds like MPB's
Except his shift works like that:
Day 1: 6am - 6pm
Day 2: 11am - 11pm
Day 3: 2pm - 2am
Day 4: 10pm - 10am
Day 5: Off
Rinse and repeat
Those hours mentioned are not inclusive of OT hours and him
working on his off days
