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.
Best Answer
The drink parallel of famished is parched.
Dehydrated is a more clinical term, and would be parallel to malnourished, I think.
Both famished and parched can be used in both formal and informal contexts, although they're frequently used with a bit of hyperbole implied, which skews them toward the informal.
There are also a lot of idioms out there to signify extreme thirst, such as the "spitting cotton" one mentioned by CopperKettle, but if you're looking for the most straightforward parallel to famished, then you really can't do better than parched.