Lately I don't know why I forget my administrator's account password and I eventually get blocked. I have read the solution sometimes and I have to search for it again. Anyway, I am blogging Zaigham's (aka zi) solution on MODx forum so I can also refer to it whenever I get blocked again. Find his solution below:

You need to have access to phpMyAdmin on your host, if you have not then ask your service provider.

• Now open phpMyAdmin.
• Select your database from dropdown list in left menu of phpMyAdmin. ( e.g. modx )
• Now, you see the list of tables displayed in left menu.
• Find table name with "table_prefix_user_attributes". ( e.g. modx_user_attributes )
• Find your username in the list.
• In your username row, you will find field named "blockeduntil" and this field contains 10 digits value (e.g. 1116602445)
• Edit the field, and set the value to "0" (zero).
• Exit from phpMyAdmin, and you are done.

Best regards.

This shouldn't take you more than 5 minutes like he said. It worked for me, I am sure it would work for you too.