It's interesting, I'm a mathematician, so obviously I write a lot (even if it's mostly not in the context of sentences) and all my colleagues/peers also write a lot and the stereotype is that math people have terrible handwriting, but by and large we don't in my experience. It really seems to me that just the action of writing characters all day every day makes your penmanship good. (Well, so, I don't mean good as in beautiful or easy to read, necessarily, I mean good as in fluid and consistent, neither of which this unfortunate specimen of handwriting is.)