If your device won’t boot up, reboot it while holding the volume up key. This will disable all extensions and allow you to get into cydia to solve the problem. Remember this so you do not have to restore to solve problems. (This is only if your device will not boot like you are stuck at apple logo. Otherwise, boot your device up normally).
Now that the jailbreak is out, this will help some of you jailbreakers do a couple of simple things that will protect your jailbreak and help you in case of problems later down the road and prevent having to restore to solve a problem. Remember, once Apple turns off signing 6.1 firmware (like on a future update), you may not be able to restore in case of problems without losing your untethered jailbreak. Therefore, these things will help you in case you do have issues as well as preventing some issues.
1) Remove the “reset all” button in settings. This button will make your device unbootable and you will have to restore. The easiest way to do this is to simply install “ResetAllKiller”. If you’re on the idevice now, you can get there by clicking here.
2) Remove the software update button in settings. This also removes nagging notifications that a pending software update is available. Clicking software update seems to put your device into a non-bootable state if your device is jailbroken. Do this by installing “Software Update Killer” from cydia. If you’re on your device now, you can click here to load cydia and get there. This is also solved by updating the latest jailbreak updates in cydia, but the added protection from software update killer doesn’t hurt.