On Writing

Last night, having self-medicated my cold with pink drink (which works!) I found my brain was too active to get to sleep, so I ended up scribbling notes for exciting new SFish novel-thing. Today, of course, I find it is the same old plot that permeated nearly all my SF short stories -- character goes mad with help of technology -- and thus will probably not bother writing it. The scenario is quite interesting even in the cold light of day, and I'd like to do something with it: but not this, and not yet.

Questions for writerly types (and anyone else with thoughts on the matter):
- do you end up exploring the same themes over and over?
- if you have a tendency to write the same story over and over, how do you stop?
- am I being unnecessarily reductionist?
- how do you plot? ("Where do you get your ideas?")