We can learn from books, we can learn from teachers, but we can also learn from the past. Some of the organizations I've worked for never look back.
I'm currently reading DEC is Dead, Long Live DEC* by Edgar H. Schein. This passage really struck a chord with me:
"The focus was on moving forward, not on diagnosing the reasons for past events... As we will see, lack of reflection later allowed many inefficient processes to survive and prevented some crucial learning."
Examining our mistakes doesn't feel good, but we've got to do it. I've certainly observed engineers repeating the same dangerous practices that have burned them before. I'm sure I do it too. To get better we need to measure the past and adjust the present. If we don't consider our mistakes, we won't know what to fix.
When we find a problematic practice, we must change. Sticking with our habits feels comfortable and safe, but it isn't. Changing bad practices probably won't expose us to more risk than keeping them.
* You can help me and my publisher by buying the book using this link: DEC Is Dead, Long Live DEC: The Lasting Legacy of Digital Equipment Corporation. In association with Amazon.