Re: Your ONE piece of wisdom...
When sailing, before doing a task, run through mentally how you will perform the task, what might go wrong while performing the task (mistakes you could make, accidents, what could break, how you could get injured). Think about how you will perform the task several times mentally before actually doing it. Determine ways to reduce risk of accidents and injuries as well as mechanical failures. Think about what you will do to recover if somthing on your "things that could go wrong" list really happen. Do you have everything you need to recover? If not, maybe you are not prepared to perform the task. Sailing is basically risk management.
You should actually think about this prior to leaving the dock.