I tend to be really great at creating crazy passwords, especially for Admin access to a site I'm building.
That also means I'm really great at forgetting the password or forgetting where I stored the password.
If you have forgotten the admin password to your Umbraco site, have no fear! You can update it directly in the SQL database or try a few options.
Log into your database and change the hash for the admin user password to:
Then login using the password: admin12345678
If this doesn't work, it could be due to the password length requirement introduced in version 7.6.0.
You can reduce the mandatory length by changing this value
<add name="UsersMembershipProvider" type="Umbraco.Web.Security.Providers.UsersMembershipProvider, Umbraco" />
Install a simple tool called 'Umbraco admin reset' that will reset the password for you. Get it here: https://our.umbraco.com/packages/developer-tools/umbraco-admin-reset/
The username will be reset to Admin and password to Admin1234! by default. Make sure once the password reset works and you can login that you change the password immediately.
If all else fails, you can reinstall Umbraco and hope for the best, but that will most likely cause a data loss so be prepared.
Let me know in the comments if these options helped!