Why Am I Already Sad That It's Over?

Ever since I was a kid begging my mom for just one more night at a sleepover, I have hated when a good time comes to an end. I constantly catch myself starting to mourn a great night out or a relaxing vacation while I am still in the middle of enjoying it. We all know that sudden wave of Sunday dread before Monday even hits, or the stress of post-vacation laundry while we are still sitting on the beach. Why do we interrupt our own happiness to count down the minutes we have left? I am working on staying present, soaking in the current moment, and enjoying the laugh right in front of me instead of worrying about the goodbye.