lol..... i once saw a documentry on happiness and they found that people have a base level of happiness and no matter what happens they will be just as happy..... so if someone wins the lottery, but is a miserable person it won't make them happier. and if you are a happy person and lose your legs, then you will be just as happy.
the point of the documentry is to show how what we need to change is our out look on a situation more so than the actual situation.
i guess this kinda contradicts the quote, but i think that it is more of an extension of it.... we can over come any obsticle with a positive out look and the worse the situation the better practice we are getting at learning to be positive.
hopefully that makes sense...