Theory vs Practice and Experience

There are two great quotes that I absolutely love: "In theory, there is no difference between theory and practice.  In practice there is." and "Experience is what you get when you don't get what you want."  Both really imply that Practical Experience is important.

As I was packing several USPS Priority boxes today, I just realized it's a great and simple example of both quotes.

In theory, small USPS Priority boxes come with self-adhesive flaps and glue holds them reasonably well when you close the box.  Yet in practice, in spite of the glue, flaps sometimes detach.  Plus, they do not detach immediately, but rather after some time.

This problem does not become apparent if you quickly close the flaps and ship the package, so theoretically, it seems like everything is designed well.

When I had a sales business, we shipped 48,384 such priority packages.  Pretty early, this problem was recognized and we started putting Scotch tape over each flap just to make sure box does not open in transit.

In theory, it looks like an unnecessary step.  Yet, in practice it is necessary to reduce delivery problems.  Use of this extra step comes from basic practical experience.