I'm a founder. I think rationality training has helped me in a few major ways:

• I have internalized that "nothing works or fails by magic" -- I expect that there is a mechanism of action for pretty much any process, and I just have to understand it, and I've started building a toolkit for generating these understandings/models.

• I have started to become more strategic. I still fail at this in many ways, but these days, I often think to: look at the bigger picture; look for alternate routes to achieve my goals; consciously consider whether my current goals are worth achieving, or whether they have become lost purposes.

• Communication: Asking for examples from my cofounders has become an ingrained, extremely common habit when I'm not sure I understand them. I also often address the meta-level of communication, often asking "why are we having this discussion?" or observing "this meeting isn't going anywhere".

• Not trusting myself: I set timers, I put things on schedules, I write things down, I block myself from websites. I know the ways in which my brain isn't as awesome as I wish it were, and so I take effective steps to patch these weaknesses.

(I'm going to go write a blog post about this now, because it seems valuable enough to keep.)