I shouldn't have been so rude in the post above so i'm sorry. I've been in your situation too so I know exactly where you are coming from. When you have a video that you think MIGHT have a chance at going viral, all of a sudden your brain starts to go crazy and you get really excited and you blow up how great the video is in your head. In your head, you envision getting millions of views but in reality the video is just mediocre....not bad....but not great.
What I learned, never expect a video to go viral. It just happens so don't think about it too much. Just focus on making quality content and getting a decent following.