Ditch it. Go away and do something else. Weed the pavement outside or potter in the garden. Fix hoover or put that shelf up. Go for a walk. Ring an old friend. Do anything but tunes. Tunes are about what you're feeling and thinking and if nothings coming it probably means you're not thinking or feeling enough so get out there and exsperience something however mundane it might be. Just make it different to sitting at your kit staring into space. Switch off the internet for 2 months. Worked wonders for me. Stops you getting bogged down in music politics so you're free to express yourself without worrying what's cool this week.