It happens, just don't let it get to you get the lightning finished and anything else becomes a bonus build, sometimes builds just fly together thanks to the kit, the build, the inspiration driving you and the circumstances to allow you pull all that together with minimal interruption or distraction.
Daft really when not working you can't get much done as you have the time but feel guilty at having it and try to focus on getting a job, but when working you don't always have the time, the energy or the inspiration so again struggle. Experiencing exactly the same, I have the model room I have the builds but after a day sat in front of a PC, the eyes or the body feels tired and you just want to turn off and chill out.