Trying to bury the rail and kill it on too small/weak a wave. Sometimes you just have to do flat turns, no matter how badly you want to lay down a HACK. I've blown more waves on that first top turn more times than I care to count. Usually happens on one of the first waves of a session, when I'm overamped before I settle down. It especially sucks when it's the best wave of the session... you can't get it back... you blew it and fell off like a kook on the wave of the day.
i'm a lazy paddler. i ride thick boards, i take off late instead of paddling early, i get out and walk rather than fight the drift, i obsessively time sets before paddling out.. i wasn't like this when i was young.
Feet Placement. I for some reason usually ALWAYS have too wide of a stance. I don't know why it is or wtf to do about it besides try to fix it while im riding the wave but moving your feet around trying to race down a line is not the best use of the ride. sooo many turns and snaps kooked out. ahhhh
the worst thing I do is the occasional double arm paddle- it never works and looks super kooky. I've gotten away from it almost completely but if I'm having a melt down session it comes back to haunt me.