Being in the mood to write, like being in the mood to make love, is a luxury that isn't necessary in a long-term relationship. Just as the first caress can lead to a change of heart, the first sentence, however tentative and awkward, can lead to a desire to go just a little further.

Creativity - like human life itself - begins in darkness

Judging your early artistic efforts is artist abuse.

Constant work, constant writing and constant revision. The real writer learns nothing from life. He is more like an oyster or a sponge. What he takes in he takes in normally the way any person takes in experience. But it is what is done with it in his mind, if he is a real writer, that makes his art.

If writing didn't require thinking then we'd all be doing it.

You don't start out writing good stuff. You start out writing crap and thinking it's good stuff, and then gradually you get better at it.
That's why I say one of the most valuable traits is persistence.