There are several situations in which imagination can overcome reason.
One of the most common ones are when you're paranoid or you are fearful of something. In this case, your imagination starts creating the worst possible scenarios that can ever occur. However, when going through the situation itself, you will actually find that it is less terrifying than what you imagined and that your were just trapped in your imagination. <span />
It is important because the sources tell you whether the article was credible. When you have an article that has bad source, you are running the risk of having, wrong, opinionated data. This can discredit you paper if you use it.
No, “alliterating” is not a word