They suggested that we hate losing something about twice as much as we enjoy gaining something! Think about it - in all walks of life it holds water. Take 'love' for example. I remember vividly when I was unceremoniously dumped by my first girlfriend! I was about 15 at the time - and 'devastated' was not the word for how I felt! Despite my father telling me; 'Cheer up son, the next one is always better' (!!!!) I was inconsolable for a week or two.
Did 'the next one' bring as much joy as the being dumped brought pain - we'll see!