I tried backing up my Galaxy S4 using this method: http://galaxys4root.com/galaxy-s4-tutorials/how-to-backuprestore-rom-on-galaxy-s4-with-root-cwm-recovery/
1st backup failed but I could still boot the phone
When backing up, it failed halfway, it failed backing up /data/.
I rebooted my phone and found that my keyboard doesn't remember my custom words anymore.
2nd backup failed and I can't start the phone anymore
I rebooted into the recovery and tried backing it up again the second time.
It failed halfway, it failed backing up /system/.
Then I tried the backup again (without rebooting) and it failed immediately saying no space on the SD card (I am not sure if it's true)
So I rebooted the phone and it is showing the boot animation forever (I waited over 30 mins).
I tried restoring /system/ from the first backup but it didn't help.
I don't even know where the problem is, how can a backup break your phone??
Any help will be appreciated.