I'm often at my most creative when I'm miserable - or at least, when I'm not entertained and stimulated. I find that physical labour such as doing home repairs or landscaping can yield good ideas and resolve questions of plot.

Even a long drive, with no in-car entertainment, helps me. If you want to be a 'producer,' it seems you have to stop being a 'consumer'.

Finally, up to 90% of what a good writer produces will never be seen. Readers see the successes, but they don't see the dross of failed experiments, complete rewrites, unfinished projects and all the rest - but you have to produce the rubbish (and have the sense to identify it, and to spare your readership) in order to produce the good bits. Don't feel bad about writing something and then binning it - that's just a part of the process!