Yes, it really is impossible to be sure if it was 'meant to be' or just plain co-incidence and 'luck'. I think each individual needs to decide on their own what it is they wish to believe. It seems most of the human populations needs something to believe in, hence so many have one type of religion or another.

Having said that, whether or not it is the placebo effect, there seems to be some validity in making things happen by believing in it. If one does not believe they will succeed in any given project, they may ultimately find some excuse to sabotage the project because they don't believe they could achieve the goal and therefor fulfill the prophesy. However, if they DO believe in it, that is the motivation to do things to 'make' it happen.