Those who want to be justified by the Law have been severed from Christ and have fallen from grace. These are strong words from Paul. But they show what is at stake: You cannot build on grace and the Law at the same time. It is one or the other.
Falling from grace doesn't mean losing salvation. It means leaving the sphere of grace and going back to the old system. A system that can only condemn you.
Today: Stay in grace. That is where life is, where freedom is, where Christ is.