@Reject: ...Actually it can be proven. I mean, weakness is why things like torture work so well.
Here's an answer from Quora by Ira Vashishtha that I think is apt at describing why humans are so emotionally susceptible to pressure:
Human aims are much more complex and it's humans that have progressed in this world. That have changed the face of the earth. It's due to our complexities. Our love, ambition, hope, determination.
Links:
http://www.evoanth.net/2015/01/08/why-are-humans-weak-our-fragile-bones/
http://thetruthwins.com/archives/scientists-discover-proof-that-humanity-is-getting-dumber-smaller-and-weaker
Also, like I said several billion times fragility is not a bad thing. It makes us human, and it makes us spiritually strong although physically and mentally we may not always be as sturdy.