The very first rule you should remember is that Steemit cannot reset your password for you. You can only recover your account if you have the last known master master password. That implies you can not recover your account with private posting key. All you need is master key. If you have totally forgotten your master password then you have no other option than to say goodbye to your account.
Further, you have time till 30 days to apply for stolen account recovery in case your account was hacked and password changed. If you had the last known master password with you, then you can easily change your master key after attempting recovery.
It is always better to use the same email you used to sign up your account on Steemit to put an account recovery request. This is likely to speed up your recovery process. This makes it easier for Steemit to verify you own the account.