Essentially, everything that happens to you happened because it was going to happen inevitably. For example, someone is born who has extremely athletic genes ... that person eats well and flourishes into a budding athlete ... that person was also born with certain personality traits such as being a very determined person ... his/her parents work with that determination to help if flourish etc. The final product: a successful athlete. Similarly, another person could be born with similar or better athletic and determination genetics but be born into extreme poverty and who does not have parents that are constructive. As a result, this person begins dealing drugs and goes to prison and becomes a lifetime criminal.
Its a nice sentiment to believe we have control of our destiny, however the vast majority of scientific research regarding human and animal behavior suggests that we do not. What's the point then you may ask? Or if everyone thought that, wouldn't everyone not care about their life? The answer is no .. while people may be able to grasp the concept of determinism, they are still endowed with genetics and an environment that prevent them from giving up and pushing on despite knowing that things are determined ... i.e. they're along for the ride.