One of the key elements of human behavior is, humans have a greater fear of loss than enjoyment of success. All the academic studies will show you that the fear of loss of capital is far greater than the enjoyment of gains.

This quote means that people tend to feel more fear and anxiety around losing something (like money, for example) than they experience joy when they gain something. Many studies and research have shown that people worry much more about not having something than actually getting something. This is because, usually, humans equate loss with a greater degree of pain than they do with pleasure obtained in gaining something.