No I didn't break her. I bought her from some travellers as "ride and drive". She was actually raced round Appleby (as they do) pulling a cart and was still shod when I got her. Apperently she had been pretty roughly treated but she is the sweetest most obliging animal - maybe just appreciates that I don't shout at her, hit her, or generally push her around. In a way I've been very lucky as mules are notorious for taking advantage if they can. I am a complete novice rider, but she just patiently stands there while I fiddle about with her bridle and saddle, then waits while I get on and then calmly walks round the field.
So, if you are starting breaking your's from scratch there are some excellent articles by Vicki Abbott (think that's how she's spelt). If you google her name, or calkinsart (who do the website) she has a real understanding of mules and explains a lot about how they think.
It is said that you have to train a mule the way you should train a horse. You tell a horse, but you negotiate with a mule. But you've probably found that out already!