your skull

asleep or awake, working or eating, indoors or out of doors, in the bath or in bed — no escape. Nothing was your own except the few cubic centimetres inside your skull.
-George Orwell, 1984

it's true. take a look at what events have happened to you recently. could you stop all or any of them from happening? maybe hypothetically you can stop something from happening, but in all surity, nothing is 100% under control. if you think otherwise, try playing the "what if" game. for every situation, there's something that could potentially put us out of control of our own lives. as stated by georgio, the only bit we can control is the few cubic centimeters inside our skulls.
While most of us consider Descartes a total whack-job for wrinkling the grey matter over the most basic if>then loop ("i think, therefore i am"), the fact remains that he was right. the reason this loop is so important is that, setting aside cases of insanity and the possibility of predestination, this just so happens to be the only thing we can control.
what does all this mean? simply that the world will do what the world does, and we need only to make the best decisions we can.
oh, by the way, read 1984.