My worst habit by far, is casting Soul Fire when I switch targets.  I have it so ingrained that I lead off with that for the buff that I don’t consider I already have the buff and it’s a wasted cast.

Next I don’t clip my dot’s correctly in the Cataclysm way.  Technically speaking we can and likely should cast before the last dot because that leads to higher uptimes and doesn’t affect the DPCT of the spell thanks to the new mechanics.  I still let mine fall off and recast right after dropping.

I’m terrible at cooldown management which is now a big problem for warlocks.  Between Soul Burn, our Infernal, and Demon Soul I’m left at the end of a boss fight wondering why I didn’t use any/all of them.

I need an addon to help me remember the 25% change my priorities rule.  I get tunnel vision and don’t realize it until the boss is at 10%.

When I flub my spell priority I have a horrible time recovering.  Generally it’s six miscasts before I figure out what the hell I’m doing and get back on track.

When we had the spellstones, I was awful at remembering to keep mine on my weapon.  There’s one mechanic I’m glad is gone!

What about you?