Db:
<<You'd be surprised at just how quickly a hospital or lawsuit can eat up 200k.>>
Exactly. Personally, I'd need many times that amount before feeling comfortable enough to quit my "day job." Not only should you account for possible tragedies like Db mentioned, but you also have to factor in increases in the cost of living/inflation. 200k in 10 years won't be worth what it is today (assuming we don't go down the road of deflation). If you plan to start with a nest egg that is just large enough to generate a comfortable living today, and you don't plan to grow your trading account as you go, then you'll be disappointed down the road when your earnings won't buy as much as they used to.
Jason