User Accounts has the ability to reset the password to something that you choose, so you could make a new one that you could be certain of.
EDIT: I'm curious, because if you are uncertain of your password, that must mean that you have it set to not require a password when first booting up to the system, which is where I generally would prefer to have the security. The only exception for me is on my HTPC, where I feel that it isn't necessary. If you don't need a secure login on boot, why do you need it just to go into Sleep Mode?
I know that it isn't the best idea to force a restart, but if you somehow got locked out in Safe Mode, a forced restart would bring you back to the regular login screen, but of course you would need the correct login data for that to give you access.