What lessons, what lessons? There are always new things to learn, old things to remember.
When doing inventory work, here are the basics you should have, beyond your digital or paper reference:
3/ blade (to open the box).
4/ packing tape, tape gun (to close said box).
Be methodical; always methodical. Don’t rush. Take your time.
Things may not be obvious. Items may not be where you expect them.
Stay with the count. And remain humble.