In Bird by Bird: Some Instructions on Writing and Life, Anne Lamott provided some auspicious advice about quieting negative voices in your head so that you can get down to work (among many other things; if you want to/already write, I cannot recommend her book highly enough).
“Close your eyes and get quiet for a minute, until the chatter starts up. Then isolate one of the voices and imagine the person speaking as a mouse. Pick it up by the tail and drop it into a mason jar. Then isolate another voice, pick it up by the tail, drop it in the jar. And so on. Drop any high-maintenance parental units, drop in any contractors, lawyers, colleagues, children, anyone who is whining in your head.
“Then put the lid on, and watch all these mouse people clawing at the glass, jabbering away, trying to make you feel like shit because you won’t do what they want—won’t give them more money, won’t be more successful, won’t see them more often.
“Then imagine that there is a volume-control button on the bottle. Turn it all the way up for a minute, and listen to the stream of angry, neglected, guilt-mongering voices. Then turn it all the way down and watch the frantic mice lunge at the glass, trying to get at you. Leave it down, and get back to your shitty first draft.”