My motivation and nterest goes very much up and down, comes and goes.
I can get head over heals into a project, building, planning etc... and then the fun and excitment of it is just gone ?!?
The project sits on the bench unattended for weeks because of lost motivation.
Then I simply wait for the motivation to return and I feel powered up to continue.

E.g: Just finished a 4* and total building time was short, but due to a "motivation gap" in between construction and covering, the whole project took me almost two months.