just do it
Remember that if you have even just fifteen minutes, you can get something done. Don't mislead yourself, as I did for several years, with thoughts like, "If I don't have three or four hours clear, there's no point in starting."
If you're stuck, try going for a walk and reading a really good book. Virginia Woolf noted to herself: "The way to rock oneself back into writing is this. First gentle exercise in the air. Second the reading of good literature. It is a mistake to think that literature can be produced from the raw."