I love this video, it reminds me of the speech Steve Jobs gave to Stanford students which inspired me no end. I am not sure yet that I have stopped to think about what I really want to do, I actually think that you have to know yourself very well to actually work out what would make you feel fulfilled in life. It's a tricky one but as this is not a practice run, it may be one spending some time on.
Once you've figured it out you need courage and a lot of it, you also need no dependents or mortgages or other trappings that tend to happen after the age of 30, so if you are not there (I am!) then take a leap and dare to dream of living the life you imagined for yourself when you were wideeyed and too young to know how not to be brave.
Are you doing what you love?