There are a huge amount of morons on the road, I haven't been driving that long really I only passed my test when I was 37 and I know everyone laughs about the driving theory test but I am glad I had to take it as it makes me very aware of whats going on around me and looking for possible hazards.
I have lost count of the times I have said to my other half, watch that guy there he is going to cut in, and then the guy does, you can tell a lot about what someone is going to do from their driving style.
You can't always be right, for instance I had no idea a white van was going to take half my Zed out last year but I guess all I am trying to say is if you think "I am a good driver so I will never have an accident" then you are kidding yourself as it's all the other morons you want to watch out for