Resetting Safari won't delete your e-mail accounts you created in those web services, just the saved username and password for logging into the e-mail service (so that you don't have to keep typing it everytime you access that service). In other words, you would have to manually provide the username and password again in order to access your e-mail accounts.
Resetting isn't as bad as you seem to think it is, provided you remember that passwords for everything you access while on the Internet (e-mail accounts, forum login accounts, etc.). However, if you don't remember what the password is for a particular service, then it could be a little more difficult. Thankfully, most services like web email and forums have the option to send the username and password to an alternate account that's given when registering for said service. That option is usually something like "I forgot my password" with a link to a place where you can provide the alternate e-mail address you gave when you registered with that particular service and if it matches, then you'll receive the username and password for your account in that alternate e-mail address.
If you still don't want to reset, you can just go in manually in the preferences for Safari and clear out the history and the cache.