Since you are guaranteed to make mistakes out there, why not learn vicariously from other thru-hikers in order to limit your learning curve.
The Top 5 Most Common Thru-Hiker Mistakes
Hiking For Beginners: 11 Essential Tips
TrailBuddy
Most Common Mistakes Thru-hikers Make – One of Seven Project
Extreme Hiking: America's Best Hard Dayhikes - The Big Outside
Avoid These Common Beginner Hiking Mistakes
9 common mistakes to avoid while hiking and camping - Lonely Planet
Why 75% of AT Thru-Hikers Won't Make It (Spoiler: It's Complicated) - The Trek
7 Reasons Why Women Make Great Backpacking Leaders On the Trail — She Dreams Of Alpine
The Most Common Hiking Mistakes and How to Avoid Them