There is a dark side to the idea of an 'internal locus of control.' It creates a sense that the individual can and should manage the situation, even when the situation is totally unmanageable. I think it's a common problem among high achievers (particularly entrepreneurs), and conversely some 'resilient' people need to accept that there sometimes really IS an external locus of control before their efforts to control…
Good point, it's very important to have balance and be able to adhere to the "And wisdom to know the difference." part. I do think that it is important to have the experience of having too much 'internal locus of control' in order to get a good feel for that.
Aurelius says something like "How ridiculous and how strange to be surprised by anything that happens in life." As in, why would external events matter or be a surprise? Things happen. The only thing you can control is how you react to them and what you choose to do about them. That helps me at least. It's all about process, not outcomes. Outcome is a roll of the die, so all you can do is make sure your internal processes are sound.