I'm trying to think of a word that accurately captures the idea of paranoia/over-cautiousness in a positive way.
For example, after the cloudbleed incident recently, a very small number of accounts were potentially compromised. The chance that yours was compromised was slim to none. But I wouldn't describe changing your passwords in response to that incident 'paranoid'.
I originally thought the word 'pronoia' fit this description, but it doesn't seem to mean what I thought it did.