As self-employed people, we know that being successful in this field requires a lot of discipline: I had to learn how to manage my time, make time for important things like seeking new work and invoicing clients, along with getting work done before deadline.
Creating serenity is no difference.
I've really learned that lately with my yoga practice. After a hiatus, I started a morning practice again, mostly consisting of asanas designed to loosen my shoulders, arms and back and make my hours sitting at the computer more manageable. But committing to do that every day, even when I have a deadline looming and I spend my meditation time thinking about my to-do list? That's not so easy. But I do it anyway, because I know that it develops a muscle in me that connects me to the greater good and reminds me that my job is to focus on what I can do today--not bemoan the past or fret over the future. For me, those two behaviors represent a lot of the things that rob me of serenity.
So, do it every day. Whatever it is that you find brings you serenity--whether it be a nap in the afternoon, a phone call to a loved one or a trip to the gym--just surrender to it. Know that by doing it, you're taking care of your business as much as if you were networking with a potential new client. I only do yoga for 15-20 minutes every day. But when I finish and sit down at my desk to start my day, I feel more centered and more joyous, and that can't do anything but help my work.