Whatever happens, happens for the best?

I remember when i was preparing for CAT, in the probablity class i asked my really brainy and philosophical faculty "Sir, kisi cheez ke hone ya na hone ki sambhaavna jaanne ka kya auchitya hai?" My faculty laughed it off and explained it to me later in a very philosophical manner that everything happens for a reason. The reason I am pondering over this today is that is it a mere method that human beings have created for themselves to stop questioning when they cannot further find answers to their questions and when rationality gives up. Or is it something that actually happens. Why does it happen that at times we want something and end up with something else? Or is it that we don't pay attention to things when we get what we want? Whatever it is, at times we are very unsure of whatever is happening to us, around us and fail to find the reasons. I hope time gives us the answers. And whatever happens, actually happens for the best. :)