Joined-up handwriting.
When I was back in gnome school, for quite a long time we were taught to write like this, then one day everyone suddenly stopped writing like that, yet I continued as if I had missed an important meeting or something.
Anyhoo, as you can guess, joined-up handwriting looks like shit when compared to something printed (un joined-up before you start thinking of computers), so when we came on to use pens instead of pencils (ooohhh excitment) in year 6, they made me waste my lunchtimes on a "handwriting course" before they let me use a pen.
In fact they never let me use a pen, I still did use one though.
But, that course completely threw me off, causing my handwriting to become some hideous joined-up/printed hybrid mess, and I never really managed to get neat handwriting ever again. Something I get criticised for all the time.
If I take several hours over what I do, I can make it readable to other people, but if I'm in an exam (I don't do any wordy subjects any more thank God), I'm writing so fast that it almost becomes unreadable to me.
In short, FUCK PEOPLE WHO PRINT THEIR WRITING.