Most designs come easy now, I can lay out a system that works. But then a job lands with no room to spare, every part fighting every other for space and weight and cost, and I stall. I move one thing and three others break, and I sit there feeling like the hard ones still have my number.
More people experience this than they realize.
You can design most systems, but the tightly constrained ones still defeat you.
If this sounds familiar, the Library can help you find the bigger picture.