So basically you're saying that if the following two conditions are true, you can't take 10:
1) Don't know if you'll succeed
2) Failure could be deadly (or otherwise serious)

Well, we know that #1 is not a factor. Why? Because there are skills where you never know if you'll succeed or not (like stealth), but you can still take 10 on them. If knowing whether or not you would succeed was even a part of the equation at all, then stealth (and probably some other skills) would have to completely disallow take 10 regardless of the situation. But that's not the case.

It's therefore crystal clear that it doesn't matter whether you know if you'll succeed or not. This is not debatable.

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With that out of the way, all that's left of your position is this:

Does the consequence of failure being deadly prevent you from taking 10?

Sean has already answered this: to prevent taking 10, you have to be distracted by something other than the task at hand. So far, your only response to this has been to ignore it. Why?