That is something that we all struggle with. When it’s something we’re passionate about, it tends to encompass our life.
There is no fast solution but if you do lack the self-discipline like I do sometimes, it’s best to have someone else who has an outside perspective help enforce your breaks. Setting your schedule and hours before you start working also helps to know that you’ve gone over. But as you seem to understand, it’s not a race but a marathon. Pace yourself. Also, find something that you’re equally passionate about help pull you away. Good luck!