Ending of Mr. Nobody?

The leaf at the end means that nothing really happened. That is was something that he imagined in that very split second. Remember the two lives that he imagined for himself" one n which he left his decisions by chance (crazy girl), another one where he chose everything (the asian girl) and one that happened. At the train station he tripped so he could not make a choice, that is why he blows the leaf which is always a component, just like the water. Remember when he crossed over from the life he chose to the life by chance? He gets killed. So the only possible way is to live your life where ever it takes you because we can't control it. So it was all product of that split second when he was thinking, and with that possibility gone, then the only real life is the one that happened where he did not choose or gambled, it was the life that chose HIM: that is why he finds Sarah at the end, and in that very moment the imaginary world dies.

some descriptions say it is a man reflecting on his life, another says Nemo is able to explore all possibilities of his life before he is even born....im not sure which is correct or that there is even a correct answer.