"Concepts are fictional and shouldn't be mistaken for reality"
The human mind loves concepts—because these are the products of its favorite activity: to conceive—form a mental representation of something. These representations are handy to say the least. Without concepts of things to "hold in mind" long enough to compare with what we experience, we'd have no basis for understanding. Collect enough concepts of things, and we're able to develop wondrous conceptual creations like an identity, world view, or theories about what we have yet to understand. And as our concepts become more refined and true to life, our ignorance abates and understanding deepens.
However, when our mind becomes too enamored with its conceptualizing powers, autocentrism sets in. Favoring its holographic account of things, the mind conflates its beguiling world of concepts with the real world, and can't be bothered to sort it all out.
But this is, quite literally, inviting a world of trouble.
The danger is that concepts, or the mental models, reasoning, knowledge, beliefs, and opinions based on concepts, aren't the things they represent, they're only mental activity about the things. It's all cognitive fiction. So to mistake concepts for reality, to hold something in mind counting on it to be real, is a risky game where getting it wrong is subject to very real penalties in the form of latent conflict and suffering—which in essence is reality informing us that we got it wrong. If we are privileged with a mind whose purpose is to understand reality, it's our responsibility, perhaps even our existential purpose, to get it right—and reality, conflict and suffering and all, is here to help.
On the other hand, holding our fictional account of the world loosely in mind as we study the real context of things, favoring actuality over conceptualization, as per ontocentrism, our chances of getting things right are much more realistic and less prone to adversity.