Hey dreamer1986, we share a similar circumstance (Born in 1986, solo developer). I've been working on a small hand-rolled engine for about 2 years now, and while my workflow process is far from perfect, I have adapted some helpful methods to help me along.

#1 Write everything down - On your best days, you will be flowing with many ideas, many of which you will forget, unless you document them. On your worst days, you will struggle to find concentration, so referencing previous notes helps. If I am coding something and I decide to pack it in for the night, I write down what my next two or three steps should be, so the next day I can pickup where I left off, rather than wasting time figuring out what section I was working on. I do the same for art creation and make notes on process improvements.

#2 Changing gears - On a scheduled (week)day of development, and after I get home from work, I work on 3-4 aspects (Audio, Art asset creation, design, coding). I work on each for about 2 hours, take about a 20-30 minute break between each. In this approach there IS a price to pay switching from one aspect to another. It takes me about 20 minutes to get warmed up playing music, and 20 minutes to get into drawing or graphics design. I can't however, code one day for 8 hours, then do art the next day for 8 hours, and do audio the next day for 8 hours, it just doesn't work for me. Find what kind of schedule you get the most throughput out of, and cater to that.

Also, be mindful of the tasks you shy away from (for me it's art) and tackle them as early in the day as possible, when you are still fresh. I can't tell you how many times I've scheduled to do animation frames after coding and it just doesn't happen. And I also realize I can still code when I am tired, so I push it to the end of the work day.

Just my 2 1/2 cents, just be honest with yourself about what you're good at, and what you're not so good at. Try to identify your weak points, and go after them first.

Goodluck!

Great advice, thank you :)