Ever wish life was predictable? Sure you have! Well I just thought of way of making predictability plausible!
Oh I really do hope I didn't get your hopes up. My justification is hypothetical and involves amateurish science. Here I go.
Anyone who attended highschool would know a bit of science. They might not remember or even have understood most of it. But they will have some idea regarding it. In layman's terms science involves the study of us and our surroundings. Now, this study helps us understand how objects react to changes. Once we've got that figured out, its easy to predict what change would occur in an object when subjected to that change.
For instance, an object at a particular height will fall under the force of gravity if not supported sufficiently. If it were to fall, we can predict its position from the ground at each instant by our basic laws of physics. Isaac newton discovered the phenomenon of gravity. On further study of objects under free fall, he came up with laws that govern the action of gravity on bodies. These laws helps us predict certain things.
Let me take up another branch. Chemistry is full of chemical reactions. These reactions were put together on study of components under different conditions. During any reaction, we can predict the state of the reaction, temperature, the phases present, the composition of the components in the reaction.
Its clear that due to our extensive study, we can predict certain things in a chemical reaction. Now let's apply it to a larger scale. The universe began with the big bang. The big bang is nothing but a chemical reaction. So, in other words, everything in this universe is a chemical reaction. Even the lives we lead are chemical reactions. So, if were able to study the entire universe, we'd be able to predict its characteristics at every instant just like we do in chemistry. Ergo, we'd be able to predict our lives.
What I've said till now is only hypothetical. In our chemistry labs, we can entirely study a reaction only after its completion or on reaching a steady state. The universe is vast and is still growing. Life on earth is still developing. Since the universe is no where near a steady state or completion, we cannot conduct a complete study about. Hence making life unpredictable.
Maybe one day we will be able to predict life. "The theory of everything" which many scientists including Stephen Hawking are working on might actually succeed in doing so. It would be marvellous if we new what the future held!
But think about it. If life were to be predictable, we'd be able to lead an idle life. We could avoid mistakes and there would be only success. Basically it would be a roller coaster that just kept climbing up. Now, where is then fun in that? I might want to predict what will happen in my life. But I want it only by a wee bit.