Word for knowing what to do and not doing it
If I am not mistaken, the word you are searching for is akrasia. See this related question or Wikipedia
Factors that lead me to believe this are
- It is of Greek origin
- It describes a state of mind or human condition as you asked
- It is related to Plato
To be honest I can not really add anything meaningful further than Wkipedia, maybe the headline definition helps as a motivation to read the article:
Akrasia [...] is described as a lack of self-control or the state of acting against one's better judgment.
I sincerely hope this is the word you are searching for, as I just performed a significant search effort after being in the same situation as you and being bugged out several weeks by not being able to remember the word :D
In dialectical behaviour therapy, I learned about willfulness. It can apply in that it affects one's willingness to do what one knows one ought to do. Another word: Procrastinating. Also: Uninvested. Apathetic too may apply. "Conflicted." "Frozen" "Undecided" "Scattered" "Distracted"