I often think about survivor bias. Like, we see a lot of old people. Thus we assume that we'll probably also grow to old age. At least I did. It was only when my wife had cancer that I realized that all the dead people just aren't around anymore to tell us that they died. We only get to see the survivors.
To drive this home, here's something I overheard on IRC: "You always hear about dolphins saving people from drowning, but you never hear about all the people dolphins have dragged out to sea."