Buddhists say everything is changing. They say that from observation because everything is changing. They say it as a means of comforting those suffering from current trials and tribulation. And, they say it as a means of encouraging focus on the eternal and unchanging.
On a more mundane level, for one reason or another, I move every few years. New York to Colorado to North Carolina to Oregon to West Virginia. Each move is accompanied with moving from one home to another. Typically, I go through all my possessions and downsize. Old things go. Broken things go. Things I don’t like go. Things that weigh too much for their value go.
With each move, I typically leave a job and friends. I remember the good times spent socializing with interesting people. I think about the places I still want to go in that locale. I think about my house and how it has become a home, the changes I’ve made to it, and how fond I’ve become of my neighborhood. I know all the good reasons for going, but I feel sad to be going. I promise I will come back and keep in touch. Frequently I do, but it’s not quite the same.