self-neglectful

I default to living in my own head, and without external obligations/input to break that up, I can become reclusive, self-neglectful, etc.

The Nervous Breakdown 2010

She was forty years old, graying, sallow, and self-neglectful.

Incubus Arensberg, Ann, 1937- 1999

Greece, like some big, lax, self-neglectful person would be an easy prey to any well-knit adversary really at unity in himself.

Plato and Platonism Walter Pater 1866

The man who risks or sacrifices his life for the public cause, is rewarded with the testimony of an approving conscience; but persons who wantonly defy the necessary, though atrociously exaggerated, precautions of government in the matter of property, at the same time that they commit an alarming hostility against the whole, are, as to their own concerns, scarcely less absurd and self-neglectful than the man who should set himself up as a mark for a file of musqueteers to shoot at.

Caleb Williams Or Things as They Are William Godwin 1796