Virginia Wolfe had it right with regard to the difficulty of writing with multiple competing obligations and the lack of a personal space to write in. She used the illustration of Jane Austin, who had the great good fortune of a good income and a supportive family to help her bring her amazing pieces of fine literature to fruition.
I am not the only writer to fall prey to this dilemma. Over the course of my adult life, I have found times when I could be extremely productive, and others when I have gone weeks or even months without writing anything of note. Talking to my many friends who write, they report similar issues.