This quote by Samuel Johnson describes a situation or object that is in the worst possible state, having been neglected or mishandled at every stage. The repetition of ‘ill’ emphasizes the extent of the damage or neglect. It’s not just bad; it’s as bad as it can possibly be, having been poorly nurtured (ill-fed), badly ended (ill-killed), inadequately maintained (ill-kept), and improperly presented/displayed (ill-drest).
In today’s context, this quote could apply to any number of situations where things have been consistently mishandled or neglected. For example, you might use it to describe a business venture that failed due to poor planning, execution and management.
In terms of personal development, this quote might serve as a warning against neglecting one’s own growth and well-being in all aspects – physical health (being ill-fed), mental health (being ill-killed metaphorically through stress or negative thoughts), emotional well-being (being ill-kept by not taking care of oneself emotionally) and presentation skills which includes communication skills and self-confidence (being ill-drest).
So essentially, for optimal personal development one must strive for balance in nurturing all aspects of their being – nourishing oneself properly physically & mentally; ending negative habits/thoughts effectively; maintaining good emotional health through self-care practices like mindfulness & meditation; presenting oneself confidently through effective communication skills & positive body language. Otherwise they risk becoming “as bad as bad can be” in terms of their overall wellbeing.