Use the Keychain Access utility (/Applications/Utilities) to store things that are really important, and use applications that are aware of the Keychain. This

Use the Keychain Access utility (/Applications/Utilities) to store things that are really important, and use applications that are aware of the Keychain. This encrypts only a small amount of data, yet the system prompts you when an application tries to access it without permission. I haven't really given FileVault a fair shot, but after I heard years ago that (the first version of) it had a bug that could make user data unrecoverable, I wasn't eager to try it.