People's behavior is largely determined by forces not of their own making.

Our behavior is determined by the our nature and attitude. While Genes contribute a little in shaping the nature of a person, there are various other factors largely influencing the nature and attitude of a person. For instance, the physical conditions and lifestyle in ones childhood and growth years, the values and morals imbibed by family members, teachers or guides and the set of experiences person has been through. All these factors play key role in determining ones behavior in particular situation.

Most of the times our behavior at an instance is the result of combination of earlier experiences and our perspective to view those experiences. For example, a beggar's kid who has lived a wretched life will be grateful if you offer a burger. However, a rich kid might reject the same offer and demand for another delicacy. These contrasting behaviors are due to their lifestyle which they are not responsible for.

In accordance to the claim, most of our experiences determine our behavior in future. For instance, if you generously donate to a person who collects money for charitable organization, but later find out that it was a hoax, in future you will resist to donate anyone or at least you would not be as generous as earlier.

However, one might still donate as generously as he did earlier owing to the philosophy that 'even if 9 out of 10 are cheaters, there might be one genuine'. Hence you would continue to be generous. This is a difference in attitude varies from person to person. Even this attitude to large extent is a result of the morals and values imparted to the person time to time by his family and friends.

To summarize it all, We can safely say that a person's behavior is a consequence of various factors which he does not govern. Not that all the factors are not created by him, but most of the factors are controlled by different experiences, family members, lifestyle and so on.