Because the smarter you are, the more you're aware of how little you really know. One of life's most important lessons is to take a moment before you speak, because what is very true for a lot of people is that the smarter you get the less you speak.
Who else is guilty of this? I'm pretty sure I've used every one of these at some point. Truth is that there are no excuses when it is something you want bad enough. Let's make 2015 the year of no excuses.