In this situation I choose to believe that I subconsciously spotted it would cause doom and subconsciously screwed it up so that the doom would be averted, and was master of the whole situation all along.

I agree. If I was Simon I would be congratulating my subconscious for appropriate self-sabotage.

Yes, thirded!

In principle I incline more towards the opposite response of criticising myself for both errors, on the not entirely unreasonable grounds that in future I would like to do better at picking things to do and get right the things I do decide to do. It's just that the two conflict in my head just enough that I find I have to concentrate on one of them at a time...

In terms of learning from experience, this is certainly correct. An extreme example would watching someone trying to solve a maths expression, busily cancelling the 6s out of "16/64" and making multiple conceptual mistakes that all cancel out to give the right answer. It's probably correct to give them no answer.

Whereas in your case, it's sufficiently complicated that you can't be SURE the errors are coincidence, it's possible that "subconscious sabotage" was an exaggeration, but maybe you tried to avoid the bad consequences, and that led to messing up the implementation.

I'm inclined to count fortuitous outcomes positively :)

What do you mean, 'in my case'? I don't think I said anything about what my case was! For all you know, I could have cancelled the sixes out of 16/64 :-)

:) I'm sorry, I read that into the way you described it, but I admit it was mostly just assuming :)

Clearly, the subconscious is a genius!

does this happen often? i can't even think of an example. i guess i'll be alert to it next time it happens to me.