For security reasons, if you enter an incorrect password sufficient times when logging in, you will lock your account.
A colleague with 'Manager' rights can unlock your account via the individual staff members page.
To do this they will need to go to the relevant staff members page, under Admin > Company > Staff and click on the relevant staff members name. A warning will be shown at the top of the page:
They then just need to click on the 'Unlock Account' link on the menu on the right and confirm:
Once your account has been unlocked, if you still can't remember the password then you can reset it via the 'Forgotten your password?' link on the login screen: