No matter how much you think you know, you don't.
I spent hours, even days studying pre-draft rankings, weekly matchups, season predictions, all leading up to the day of the draft. I had my top players for each round and was fully prepared to dominate the 2014-2015 fantasy football season.
Who knew Calvin Johnson would score >5 points in Week 4? Or that Mohammed Sanu would throw for a TD in Week 3?
Perhaps, this applies to life. No amount of study or preparation will ever prepare anyone for the unexpected twists and turns on the roller coaster of life (also, why is the game of Life a road trip when it should be a roller coaster?)
The good news is that in fantasy football, you're not stuck with your draft day starting lineup, otherwise there would be some angry RGIII owners right now. You can make changes weekly, even daily. Adjustments are the only way to win.
Be prepared for change, and remember that no matter how much you think you know, you probably don't.