You're reading too much into the context around the words. While we may often speak of preparing for the worst, the words aren't inherently about negative consequences and situations.
The word prepare has a little flair of unwillingness ... On the other hand, the word ready itself denotes some negation and we are not optimistic.
Neither word carries any sense of negativity or unwillingness. We need not prepare only for bad things. For example, I have spent the last week preparing for my vacation and now I'm ready to leave. My vacation isn't "bad" and I'm definitely not unwilling to take it.
In short, if someone is ready, he simply accepts the thing but if someone is prepared he has the alternative way to come out of the situation.
No, this isn't the difference between the two words, because you've missed the appropriate meanings. As above, prepare and ready aren't about dealing with unwanted or unpleasant situations, so your remarks here don't apply.
While the gross meanings of prepared and ready are the same, there is a fine difference between the two. Specifically, one of time and expectations: ready is much more immediate than prepared, and we use it when talking about something expected to occur very soon. If we are prepared, we have gotten ready in advance, or even though something is unlikely to happen.
For example, in the linked article, it talks of being prepared for an Ebola outbreak in the US because one is extremely unlikely. Or examine my vacation example from earlier: I say I'm ready shortly before I leave, but speak of preparing during the time leading up to it.
Suppose I am putting my all money into a new business in a recession and someone warns me about the consequences, do these replies of mine mean the same?
"Don't worry, I'm ready for any consequences"
And...
"Don't worry, I'm prepared for any consequences"
These two are largely the same here. Prepared is more formal, but ready suggests a greater confidence (e.g. the common expression ready for anything) when talking about a hypothetical event. This is because of the subtext of immediacy with ready; even though you're just as prepared regardless of which word you use, if you say ready, people will hear even if this happened right now, I'm prepared to deal with it. When making the same comment with prepared, that right now isn't implied nearly as strongly.
The immediacy of ready over prepared is the reason for the differences that Lucian points out.
@StoneyB gave some good examples.
I will expand upon it by saying that "Acutally" as a lead-in word is not always appropriate and can be misleading or confusing. You should generally only use "actually" when you are contradicting or negating something that was previously said.
Examples:
A: "I thought that person was very rude."
B: "Actually, he was very kind to me."
A: "The capital of Germany is Frankfurt."
B: "Actually, the capital of Germany is Berlin."
Best Answer
This is an area where usage has gradually changed. Historically, the preference was not to use any preposition at all between at a loss and what to do. But increasingly people now insert one of various alternatives including as to, for, over, regarding, to know, etc. And if this NGram is to be believed, the first of those is now the most common form...
There's no grammatical rule involved here - just idiomatic "custom and practice". Personally, I don't find any of OP's suggested of, at, or on acceptable, but all the alternatives graphed above seem at least "credible" to me (though like most people, I would normally use as to in this exact context).