That stupidity is worse than malice.

It's a relatively uncommon moral value that I follow. Without going too much into details, I picked this up after realising that people caused me more harm through actions that didn't benefit them, than through ones that did it. And then realised that it was not just towards me - people cause more harm to everyone else due to stupidity than malice.

This has the following consequences for me:

• If I do something wrong, I can't excuse myself through "I had good intentions". I actually need to fix it, or admit that I don't care.
• It made me more lenient towards people acting on their own interests, in a selfish albeit transparent way. Including myself.
• It makes me avoid fools that keep screwing everything up, and then saying "but I thought that..." (no, you did not think - and that is the problem)

[Edited for phrasing.]