I work full-time as programmer. Out-side of working the 8-5. I usually have to spend about 30 minutes doing extra research to keep up with tech. So personal + work responsibilities can consume a majority of wake time. Learning how to manage time and make lifestyle changes/sacrifices are essential if you are looking to develop any sort of long-term side-gig.
With that said, it's not exceptionally hard since we tend to waste more time than we believe. It's a matter of developing discipline, time management skills, and just making small daily adjustments. I generally find myself about 3 hours to read and work on my comic (on a weekday), while taking care of my personal life/health, relationships, and career. As someone who is "naturally dis-organized and undisciplined" I can say it's not something you're born with, it's something you learn and practice when you're either really young or later in your life when you realize, you need to make changes.
I recommend spending less time worrying about squeezing things in and make a habit of spending 80-90% of you're efforts planning out what you're going to do and how. Usually you'll find you have more available to work with and less resistance than you originally thought. Developing routines also REALLY helps since it saves wasted time on decision making.