[ghodith]

For some added pedantry: aren't all the mistakes that a professional might make, also ones an amateur would make?

In fact, it seems like an amateur is likely to run into all mistakes more often, thereby making all mistakes amateur mistakes; unless there some class of mistake that amateurs are better at avoiding?

[digging]

There are probably mistakes an amateur cannot make because they can't penetrate the problems where the mistakes would be made.