And there are plenty of others who would benefit from this advice.
As a matter of fact, I could produce a major list of ex-clients and the vast majority had never grasped it.
The principle is very simple. But the benefit comes only from the rigorous, regular, -- even habitual -- application of it.
The principle is: always close the loop.
Here are a few examples.
If you go for an interview, afterwards you must sit down an and write up every missed question and failure. You must assess the gaps in your knowledge, or presentation and close the loop. Closing that loop might involve learning the answer to a question you missed. It might involve developing a small sample program to recursively traverse b-tree, because that's what you messed up on. It might be a matter of reflecting on all your past experiences and determining what the nastiest bug you ever encountered was -- because you drew a blank when hit with that question. The point is, that you must always close the loop. Address deficiencies so that they are never repeated. By following this policy, you will root out deficiencies and remediate them.
If you fail to close the loop, you will undercut your self-confidence. Your own mind will know, implicitly, that you didn't take care of business, and that you have a deficiency of which you have not undertaken remediation. That means, without closing the loop, you are worse off for your bad performance. Not only do you have a flaw, but you know it, and you didn't care enough to fix it, or start fixing it.
The violation of the closed-loop principle seems institutionalized in many companies. "Let's move on, " they say. "There's no point in doing a full-blown investigation of why this happened." No? Seems like the point would be identification of the problems that led to the debacle, followed by instituting a plan to avoid it in the future. Without closing the loop -- doing a post-mortem examination of failure -- assigning blame, where blame is due -- every future action is subject to the same causes. And, naturally, the same effects.
So alway, always close the loop. And of course, you can use your techno-journal to help.