A professional comes in everyday, rain or shine, and does something - whether it's perfection or well-received by critics doesn't really matter. The professional knows that you have to put in the hours.
An amateur, on the other hand, works in fits and starts and worries more about the validation of others instead of gettin his work done.
Professionals write all the time whether they're inspired or not. They know the path to inspiration begins with dragging yourself out of bed in the morning.
Amateurs only write when inspired. As a result, they don't write as often and lack experience so that their work suffers when they actually are motivated.
Doing something is a helluva lot better than doing nothing. Even if it's not perfect, you can always go back and edit. If other's hate it, you still gain a measure of where you stand and where to make improvements. Sometimes you have to just have to allow for - as an old teacher of mine used to say - diarrhea of the pen.