It is not important to worry about what you want to do as long as you are sure of what you do not want to do.
Backward thinking does help tremendously. I used to worry a lot about the forward angle and worry about finding it so easy to figure out what I do not want and never be able to quite figure out what I want. But it is quite the opposite. Knowing what you want to avoid is a certainty not to be passed out on.
From http://umang.livejournal.com/36819.html about a year ago:
In the locality of the here and now, all decisions can only be baseless. We can hardly comprehend the vast array of the multiple factors that affect us and our lives. Yet we fret over decisions so much, spend so much time and energy on them. And then we claim to have made informed decisions. The truth, my friend, is that us folks of the third rock are masters at self delusion.
But it is good that we do not have access to all the factors that we should pay heed to. The overwhelming vastness of possible choices and outcomes, coupled with the fact that no one knows what they really want is terrifying.
So we trudge along, pretending to have made the right decision looking forward ten years into the future, and believing so even ten years hence thus having the magnanimous capacity of accepting what we are dealt out.