One simple question

The question is rather simple, but I am not sure if the answer is all that obvious.
" Why do we think the way we think ? "

I recently read an article that talked about the "cosmic law" as proposed by the Buddha. According to this law, all that is happening was just meant to happen that way.It could not have happened otherwise.It goes on to conclude that one should not have any hatred towards someone for something bad that he did to you, because whatever happened to you simply had to happen and that person was merely following the cosmic law to generate that event.

Now, as a fall out of that argument can it be implied that the effect was already decided ? Then, the cause was so generated as to produce the required effect. In summary, the effect was the cause for the cause to produce the effect.The "principle of causality" is violated in this case and there remains little distinction between cause and effect.

I have read in a number of places that "you are what you think you are" and other such numerous versions of the above statement that basically translate into "You can become what you choose to become".Agreed.

But,at the cost of repitition,my simple question is "Why did we think in a particular way".Why does a winner think that he can win and on the same lines why does a loser think that he will lose.
Building upon the cosmic law, can it be argued that the winner was already chosen and his thought process, was merely in a manner, conducive for him to win ? (Though I don't know what algorithm is used to choose the winner !!)

Is it possible that we already have our destinies decided and we think in a given way in order to fulfill that destiny ? I know that sounds kind of a defeatist attitude where you are accepting that things are not actually under your control.But could it be the truth.I don't know....