It really isn't difficult.
Saving passwords and never using them makes them fade from memory, Using it every time you log in the forum reinforces it.
The "save password" tick box you think is your friend is put their to reduce other peoples work (password resets) it's not there for your benefit and it trains you to be bad at it.
Amen
I never save passwords and it amazing how many you can remember by using them regularly. Like many things that make your life easier all it does is de-skill you.