Meanings of baneful habit in English

My foible was patriotism; I was ruined by the baneful habit of trying to serve my country.

Always there were pictures and sometimes many of them, for in his later years Laurence Austin had contracted the baneful habit of extra-illustration.

He was glad to observe that for some time M. Violette had interested himself more in him, and had resisted his baneful habit somewhat.

Without a shade of doubt the chief cause of decay and death amongst youths and young men, is to be traced to this baneful habit.