With the recent jailbreak being released it can be a bit buggy and have some minor problems, however, with time the bugs will be fixed and ironed out. With that said, you may accidentally install a bad package from Cydia and encounter some problems. Thankfully though there’s a simple fix that’s been around for quite sometime, it just hasn’t become very wide spread. Continuing on, if you happen to install a bad package from Cydia all you need to do is hold down the Volume Up button while your iOS device is booting. This will cause MobileSubstrate to deactivate, thus deactivating all your installed tweaks and packages. If you have an older iOS device without a Volume Up button, plug in a headphones with volume control buttons and hold down the center button.

Enjoy!

[Reddit]