I have one cardinal rule for sports: don't go faster than you are prepared to hit something at.
Of course how you hit can negate the apparent safety factor you create by not exceeding the speed limit, which is to say you always come out of a wreck ok, but, the faster you go the more energy you have so the more injury you are likely to incur during an impact with a hard object.
That a good rule of thumb! I was mentioning in another thread, but one of my skiing rules, related to this one, is to try to stay away from solid obstacles (trees, poles, structures). Even when I see a crowded run or people who might do something unpredictable, I prefer to slow down, make it safe and then keep doing my thing ...