This problem seems to be a big problem but finding the answer was rather hard and frustrating. So, if you encrypted your Android phone, depending on the phone and ROM, you might have found out that you cannot decrypt it because in the settings there are no options to decrypt the device. (My phone is CyanogenMod Galaxy S3 T-Mobile.) Besides from this being a strange idea that is screwing phone owners over, it does serve its purpose because trying to remove the encryption is nearly impossible. Sources on the web say that a factory reset will fix the problem but they won’t. Booting into recovery and trying to wipe the data there results in the inability to mount /data and other important file locations. Attempting to install another Android ROM over the existing ROM will not work either because /data cannot be mounted. I even played around with ADB (Android Debug Bridge) but was never able to get the adb shell commands to run on my Android. These ideas came from everywhere on the web.
The solution is to use TWRP (http://teamw.in/project/twrp2). This is a really good recovery image that allows you to access your internal and external sd cards after it prompts you for your password to decrypt storage. So finally after button mashing on wiping my data and restarting TWRP a few times, I was able to remove the encryption on my device and put on a new CyanogenMod version. All my data was wiped away but I had backed it up ahead of time.
In short, TWRP is the recovery image that saved the day and my phone.