unable to unlock login keychain? [duplicate]

Everytime I start my MacBook Pro (which is set to automatically boot into my account) I get the error message "unable to unlock login keychain" with 3 options - continue (which will give me errors as I use my computer whenever I need the login keychain) create new keychain (I know this creates a new keychain, but does it copy all my keys? Or are they lost now?) or Update keychain password.

I've used the password which I think should work, but it doesn't. Now my machine auto logs in, and I get the error, and at the moment I'm clicking continue.

I've tried using keychain repair, which finds no errors.

Please: How should I trouble shoot my keychain errors? How do I fix my keychain errors? Is there any way to keep all my old passwords, or have I lost those?

If you cannot unlock the keychain then its contents are lost, they're encrypted using the keychain password.

Your login keychain and password are linked, if the login password is changed via system preferences the keychain password is changed to the new password also. However, it is possible that the login password can be changed by other means whilst not changing the keychain password.

When the system logs in it will try to unlock your keychain with the same login password - if they don't match, you'll see the error message you're seeing.

If you manage to remember the keychain password and unlock the keychain you should change your login password to match. But, as I said initially, you're out of luck if you can't remember the password.