You have learned from one mistake - that is good. One of my favourite quotes is from Bill Gates "Success teaches nothing."
One way to avoid mistakes is to learn from others. Scout out some instructors. I tell instructor-wannabes that they have to have made a lot mistakes before they can impart their experience to others.
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)