The habit of forgetfulness is considered as a bad habit, especially if it is exhibited in dharmic activities. That is, if a person is bounded to perform a duty and exhibits incautiousness towards such activities, then it maybe considered as a sin.
While enumerating that qualities that a king should not possess, Narada mentions incautiousness also
Dost thou keep thyself free from the fourteen vices of kings, viz.,
atheism, untruthfulness, anger, incautiousness, procrastination,
non-visit to the wise, idleness, restlessness of mind, taking counsels
with only one man, consultation with persons unacquainted with the
science of profit, abandonment of a settled plan, divulgence of
counsels, non-accomplishment of beneficial projects, and undertaking
everything without reflection?
[Section 5, Lokapala Sabhakhayana Parva, Sabha Parva, The Mahabharata]