Don't push it. If the inspiration isn't there on a given day, don't try to force it into being. You'll only end up rewriting anything you manage to put down at a later date. You have to allow yourself to be vulnerable in order to write expressively, so look after yourself first. Make sure you feel comfortable and safe - physically and emotionally - in your writing environment. Sometimes I cry when I'm writing - or get really angry. You need to feel comfortable enough to delve into those emotions. If you're stuck, jot down some rough ideas and let them percolate for a few days. Stress is the enemy of creativity, so try to allow yourself time to just sit still and let your imagination do its thing.