Finding the “off button”

I am now 3,000 miles from the office and my clients and their needs are a distant memory. My children, however, are not. My good friend confided to me the other night that she still worried about the choices her children were making even though they were fully entrenched in their college years. "If I could only find the off button" she said clutching her chest as if tugging on her heart.
How can a parent turn off all their feelings and concerns for their children? I am afraid that without my clients to worry about, I may end up obsessing about my children. My son just started his freshman year at the University of Colorado –Boulder and my daughter is living in Grosetto, Italy. I still feel unsettled not knowing whether my son got the stupid haircut I keep pestering him about (and provided him with the cash). More seriously, during his first week of college a student in his dorm was found dead in his room and a friend of his from high school was in a terrifying automobile accident. My daughter is at a life-changing precipice as she pursues career opportunities. How will they manage without me? I thought I was done parenting and was looking forward to having no one to take care of except myself.
Then it dawned on me. Last summer when I faced a debilitating medical condition of unknown origin, my parents were there for me every day… and I was almost fifty! Yet for many years now I thought my parents were no longer parenting me. Likewise, I didn't think I needed my parents and, shamefully, took them for granted. But, as I came to discover, they were still worrying about ME!
The next six months I promise not to obsess over the challenges my children face. They are both adults and I trust that I gave them the foundation to be self-sufficient (they are both awesome at laundry) and I am anxiously looking forward to seeing what choices they make on their own. Still, I am the only mother they will ever have and if they need me, I am only a Skype call away and can jump right into anything that is troubling them. Let's just agree that being a parent doesn't come with an "off-button"….yet, with some distance between us (and a good bottle of wine), I can find the dimmer switch. Now if I can just stop worrying about the cats.