Saw this trick on downloadsquad.com, so share this tips here on how to reset your forgotten password.

1. In GRUB message, press the escape key.
2. Select the one with the recovery mode
3. Boot up in shell until you reach the command prompt. Type in "passwd username" where username is your account username. (typing "ls /home" to bring it up)
4. Enter your new password. Confirm your password again.
5. Type "shutdown -r now" to reboot your system.