WordPress has some built in ways to reset a password, and they work well, most of the time. However, there are occasions where you find yourself locked out of the dashboard, and the “forgot password” link doesn't work, or sends the reset link to an email that is no longer active.
This video shows you how you can reset your password by directly editing the database that WordPress stores everything. I hope it helps.
DISCLAIMER: Editing the database directly can break your site. I recommend you take appropriate backups before attempting this, and I accept no liability if things go wrong.