For me, it's the general problem solving mindset. If you run into a segfault, you don't give up. You open up GDB and start getting your hands dirty.

Similarly, if your users aren't retaining or if your co-founder quits or if your investor is suing you. You don't give up, you find a tool/resource/strategy/mindset and figure it out. Over time your problem solving compounds and you've built an anti fragile company.