If you have the flexibility in your schedule to do it, start your day with something creative and inspiring. Maybe it's that novel or short story you've been working on, or a painting, or a craft project. Whatever it is, if you can, give it your first hour. It's uninterrupted time, and a good start to the day. Photo by Frederik Rubensson.
In an essay published in the journal Science (note, an essay, not a study,) Jeffrey J. McDonnell, professor in the School of Environment and Sustainability at the University of Saskatchewan, explains how hard it was for him to find time to do something for himself as well as handle his regular duties:
Despite working like a madman, my productivity as measured by paper output was meager. I simply could not find time in my day for undistracted writing. And when I did find the time after an extended stretch away from writing, the warm-up period to get back into the paper was often long, further slowing my progress.
...I've since developed my own version of this approach. I call it the 1-hour workday, referring to the short, sacrosanct period when I do what I see as the "real" work of academia: writing papers.
First thing in the morning is when I'm at my mental best, and when I'm still most in control of my time, so I now use the first hour of my day to write. For me, it's best done from home. I've developed something of a ritual: I wake up early, make an espresso, and write until I'm spent -- or until distractions like email or the day's deadlines and meetings start to intrude. This is usually about an hour, some days a little less and some days more. I've found that, like hitting a ball in golf, regular writing is easier if I tee it up. I plan my early morning writing the night before. It is in my calendar and on my to-do list, with details about which paper and section I will be working on.
McDonnell goes on to explain how the simple shift has transformed his work life, and given him the freedom to do a little every day just by setting aside a little time to get started. While he's talking about writing in terms of writing academic papers, there's no reason you can't generalise his advice to any creative or personal endeavour you wish you had more time for.
Beyond that, while the premise here is to tackle those personal pet projects in the morning, if you're not a morning person and your "best hours" are in the evening, tackle your projects then. We even have some tips to help you get things done after a long workday has drained you.