chucking tools out of your toolbag before you start is unwise

And there is another gardening analogy!

This all makes sense (don't be too assertive; be somewhat assertive, slightly assertive) and I like that line of advice. I suppose it's possible that newbie writers aren't prone to use the passive because it's been drilled out of them by well-meaning teachers; "avoid the passive" is thoughtless advice given out without much understanding in millions of classrooms. But I'm inclined to think it's just that they haven't encountered its possibilities as yet.