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This usually happens if the user account is corrupted. First I want you to try to boot into Safe Mode and see you are able to login to your account. Turn off your Mac by holding down the Power button for 10 seconds. Turn it back on and immediately hold down Shift key on your keyboard for 20 seconds and this will boot into Safe Mode. Login to your account.
If you are still unable to login to your account, then lets repair the hard drive. Turn off your Mac by holding down Power button for 10 seconds. Then turn it back on and immediately hold down Command and R keys at same time for 20 seconds and this will boot your Mac to the Mac OS X Utilities screen. From there, click Disk Utility. Select your hard disk at left column (Macintosh HD or hard disk name). Then click Verify Disk (under First Aid). If asked to repair, click Repair Disk. Then click Repair Permission.
If you are using latest Mac OS X El Capitan, then you will not see Repair Disk option in Disk Utility. Instead click First Aid button and run it. Repair if asked. Once it is finished, restart your Mac from Apple menu.
Are you able to login now ?