Sometimes plugs are really tight. Some “lug” thought that they were lugs.
It just take some experience to know if things are going to break or “break free”. If you don’t have such experience, someone nearby will have it and share.
But here are two tips.
First, make sure you torque out the plug without any sideways bending action. This is hard to explain, but a T-handle with equal length arms, and equal force on those arms, will just torque and not bend the plug. Our usual one arm wrenches apply a very large bending, especially with long extensions used to get into the spark plug well of a DOHC engine. So torque out your plugs, and don’t bend them out.
Second, if after the initial release of the threads, the threads feel as if they’re jamming while being unscrewed, shoot in some penetrating oil, and work the plug in and out until it can come out without difficulty.