Libraries really are wonderful. They're better than bookshops, even. I mean bookshops make a profit on selling you books, but libraries just sit there lending you books quietly out of the goodness of their hearts.
My rule has been, so far as I could have any rule (I could have no cast-iron rule) - my rule has been, to write what I have to say the best way I can - then lay it aside - taking it up again after some time and reading it afresh - the mind new to it. If there's no jar in the new reading, well and good - that's sufficient for me.