Just because human have more intelligent brain it does not mean the purpose of living for human differs from animals. We have goals but those goals are nothing but to improve our pleasure and the most importantly to extend the life span. On the other hand, the limitation for human to understand himself is that there is likely a circle that you try to use your own brain to understand the thinking from your own brain.
Survival is major goal as far as I can see and having a better quality of life is a luxury. Whether or not the latter is adaptable is not known to me.