First off, I'm glad everyone walked away.
Just how do ashes make a road treacherous? I don't understand that.
I do understand that accidents happen. They are unintentional, hence the term "accident". 90+% of the time accidents are the result of poor judgement - the rest of the time its because of an unforeseen event (animals, sudden heavy downpour/snow/fog, accident near you that you can't avoid). So, for the 90+% of the time, I think the point is for us to learn from others mistakes and remember to drive according to conditions which includes weather, road maintenance, road characteristics, vehicle and driver abilities.
So, I do agree that your boyfriend made an error in driving on a corner that isn't just ideal. I hope that your boyfriend, and you, take away some learning from this. I also do agree that we are human and we screw up.
I think that the point Foxhunter is trying to make is not to blame it on others, but to accept that we make mistakes and we have to accept the responsibility for that and learn from it. Preferably, we can learn from others mistakes as well, but we're not always so good at that.
I've gone into the ditch myself a few times in my decades of driving. Every single time was my own blasted fault. Or how about when I tried to drive away from my gooseneck trailer with the tailgate up.
I've caught myself lots of times driving where I make a mistake, but the fates decided to forgive me and nothing bad happened. I've had it happen when something completely out of my control happened (animal, freak weather, unbound load on a trailer going the other way...) and from pure luck and luck alone, there was no one else there so I had the road to myself to correct and get out without a scratch. And even those times, I look back and think, "Now did I honestly not have any warning about that at all, or was I just not thinking and paying attention properly?" It's really VERY rare that we shouldn't have known better.