The best writing advice I have received is to not erase. I think this is important and it has stuck with me for so long is because sometimes we write and we don't like what we've written so we "erase" that line or paragraph. I have been one of those people who does this, wanting my writing to be perfect the first time around, which it never is. By not erasing you are preventing this. Even if it's bad, keep the idea. You can always come back to it and make it better instead of getting rid of it nd forgetting it. Keep the idea, the line, stanza, whatever. Trust me it will be beneficial.