Your external hard drive is going to fail.
Every hard drive out there is going to fail at some point, the question is, when. Hard drives and CD/DVD drives are the components that fail most in computers. Why? They have bunch of tiny little moving parts that break down and fail when they get dropped or too hot.
So what...? Most of you reading this know that hard drives are unreliable, and if I asked for a show of hands asking who has had a hard drive fail, the scene would look like a bunch of teenage girls at the front of a Justin Bieber concert.
I want you to know that there is a better way to back up your data and to store the files that you don't need with you all the time.