This error is occurred after you try to logon many times with wrong password. It means that your user is locked by system.
Below is a step for administrator to unlock and reset your password.
1. Check status of user from T-Code "SU01 - User Maintenance".
If you found message "Password logon not possible (too many incorrect attempts). This user is locked!! So, you have to unlock this user.
2. Unlock user
From the first screen, just enter username that you want to unlock. Then, press button Lock/Unlock or Ctrl + F5.
System pop-up message to show you that user is locked due to incorrect logons. The message may change due to the reason of user locked. In this screen, you have to press "unlock button". Once you unlock the user, you will found that error message in SU01 is disappeared.
3. Reset Password
If you are administrator, you can reset password from SU21 by enter initial password. After this user login into system, system will ask to set new password.