Word of the Day: Reck
That's the case with 'reckless'. What is 'reck', and why does having less of it (or the loss of it) make things difficult? 'Reck' comes from the Germanic, its old English form being something like reccan. It carries the idea of 'to take care of', 'to heed' or 'to have a thought for'. If you do none of these things, then you are said to be 'reckless'.
Obviously, if you are doing all these things, you are said to 'reckon' — giving due consideration to the topic at hand. Eventually, there will be a 'reckoning' — an accounting of all the pluses and minuses of the outcome of an incident, event, or other process.
'Reck' has traditionally gone with 'rede', the Germanic word for counsel or advice. A person who is 'ill-read' is actually one who is badly advised; a person who is 'unready' may be badly-advised, or lack wisdom, or reject good advice. The implicit or explicit relationship is one of recking one's rede; to be reckless of one's rede might lead to disaster.