Note to self, on rubbing out:
As a child, you want to rub it all out ‘cos it’s all wrong! Start again from scratch or screw it up and throw it away in a fit of temper.
Later, when drawing from life, you think: don’t rub everything out; the ‘wrongness’ can only be in the relationships between marks, so you need to choose which of them to adjust. And don’t rub out before you have corrected the error, because it is a marker to work from. If you take it away you may just repeat the error, i. e. redraw the line in the same place.
Ideally, you think, never rub anything out – each mark should be a considered mark of observation worth keeping (this is a vain pose).
Then (lastly?) you recognise that the eraser is a positive tool – creating light, adjusting a line, balancing tone, making more precise etc. Taking away can be just as creative and selective and considered as adding a mark (this would be obvious if you started from the position of a carver).
And singular precision of line (as opposed to multiple exploratory wanderings) can also be worth pursuing. It’s all a matter of choice and awareness, of not automatically following a knee jerk reaction but being able to recognise that reaction and choose whether to go with it or not.