Curiosity in general. I need time to mull things over. When I figure them out I tend to get motivated in spurts. Like I have spent 2 days figuring out a layout of complex sweeping geometry that mixes two shapes in weird ways. I'm trying to figure out the order I need to create the shapes to make it work in FreeCAD and fully parametric while also integrating all of the connections needed to print as one main piece without print supports, while also fitting several external component parts and how they will be assembled and secured, and finally ways of attaching a few other panels and parts in a clean way without fasteners.
Basically, 3d printing sucks at creating traditional looking ventilation grills and vents, so I am integrating an oval and a rectangle, or a hollow cylinder and a hollow box in a way where they create a nicer gap between them.