I remember when I first started making maps. These maps were mini game maps and I loved messing with command blocks to create new unique mini games. Honestly, it's all about that passion. If the passion dies out, then building would just feel like work, and you would stop. You gotta love what you do. It would also help if you loved what you are building. Build the things you love and that you are very interested on building. Also, I recommend you create some sort of schedule, as this helped me get the work done. It's sometimes really tempting to just stop building.