How to stop doing stupid shit: minimize your unknown unknowns. How to minimize your unknown unknowns: learn the correct way to do things. Without guidance and mentorship, which is largely non-existent in software, you're stuck flailing around until you attain enlightenment (either by discovery or invention) on each thing you do. When you start the next task, you start the process all over again. Over time, you gain wisdom, at the cost of neurotic self-doubt.
There's a reason StackOverflow is so popular - it makes it easier to find the 'well trodden paths' ("correct way") along with someone pointing out caveats.
