I worked full time (40 hours per week, M-F 8-5) for the last 2 years while taking pre-req's. I took anywhere from 9-14 hours a semester. For the most part, I only took 1-2 science classes at a time, with another "easier" class. So like I took Organic 1 with Psychology. And Organic 2 with Sociology. Also, whenever I took a course in the summer, I only took 1 science course, since they're usually accelerated and needed more time devoted to them in a shorter amount of time. Like many above have said, I had to accept that this was going to take me a while. I couldn't knock it all out in a 1 year and then apply. Once I accepted that, It was much easier to give myself the time I needed to balance work and school.
Also, for my non-science classes like Psychology, Sociology, etc. I tried to take those online if possible. This cuts down on commute, and you can fit them in your schedule where they fit. You're not tied to a class time, no commute, etc. Big time saver! I wouldn't recommend taking any of your science classes online, especially those with labs, but for the humanities, English, etc. I think that is fine!
I also learned how to "compartmentalize." When you're studying/doing hw, don't think about how you wish you were at the gym, with your friends, etc. Conversely, when you're taking breaks and doing activities that you enjoy (which you 100% still need to do these things), don't feel guilty and think about how you should be studying right now, etc. This really helped me because it allowed me to stay present in the moment, which made me more productive/efficient at studying, but also allowed me to get the important benefits from still doing things I enjoy. You NEED those breaks. There is more to life than trying to get into medical school. And if you lose sight of those good things in life, is what you're pursuing worth it?
OH, and 1 last thing- if you're up late studying and you're really tired, go to bed! The sleep will be WAY more beneficial than the 1 or 2 facts you may or may not learn, that may or may not be on your test the next day. Your first inclination is to stay up and push through, but when you have to go work 8+ hours before going to take a test that next evening, it's not worth it. And it will take you much longer to catch up on all the lost sleep, affecting much more study/homework times. This is at least how I looked at it!
This is just my 2 cents though, for what it's worth! I did end up with a 4.0 (DIY) post-bacc GPA across 50 credits, kept my same job/salary so I could afford to pay for these classes, went to the gym multiple times a week, and still had time for fun things, my family, and my friends!