A user “novice” combines small disasters, does not know what he did and don’t know how to fix errors.
A user “evolved” combines large and small disasters, almost always knows what he has done and is able to hide their mistakes.
A “junior sysadmin” is capable of doing many more disasters, but he knows what he did, he knows how to correct some mistakes and he knows who to ask to correct the errors that can not correct itself.
A “senior sysadmin” combine few disasters, but when he makes them are big, he knows how to correct the mistakes and knows that unless he is able to correct, no one will know it and so will have to learn / invent another senior sysadmin trick.