“Nostalgia can not be sustained without loss”

http://www.healthyplace.com/blogs/buildingselfesteem/2013/09/behave-like-an-adult-build-self-esteem/

As people grow older we experience lose and gain. Oftentimes, in order to understand what we have lost, we must lose it. Whether it is someone we love or even the simple wide-eyed wonder of being a child.