Potency limits act.

I've read multiple Thomists and I feel like I'm not getting something. I've read that act is limited by potency because every particular thing in act doesn't fully instantiate perfection. So a drawn circle is always a bit crude when compared to the abstracted form of circularity. In this way, the potential to be circular limits the perfection of act for circularity. Also anything that is composed of potency and act is always limited. For instance, a vase is limited to a particular place and condition--be it on the shelf, on the floor, on a table, cracked, smashed, polished. In this sense, its potencies limit it to a specific place and condition.

Am I missing something?