Our brains are stupid when it comes to calculating probability. As a result, we all have this fuzzy idea that if something can happen, it probably will. And we think this, while having no idea what "probably" even means.
This is why millions of high school kids think they're going play pro sports when they grow up, even though there are only enough available jobs for a tiny fraction of them. When the news says an asteroid may hit the Earth in the next 10 million years, people will watch the skies suddenly sure that an asteroid will hit that day.
Read about all five fallacies at Cracked. Link