I would say a big part was that I was very interested in the project so even when parts of it were difficult to figure out I kept wanting to come back to it.

The other was breaks. I didn't do this all in one stretch and instead did it in small chunks over time. I wasn't trying to ship a final game or finish as quickly as possible so the time scale was very relaxed.

Then the last was to make sure the process stayed as enjoyable as possible. If I was getting stuck on a problem or if a particular path really didn't seem to be working, I preferred to either take a break from the problem and come back later or find new sources that helped me see if in a different way (or both).