A Dead Battery
If you run your device into the ground, meaning you use it until the charge has entirely run out, you run the risk of destroying your battery. This is because a drained charge forces your device to shut itself down. When this happens, your battery is permanently weakened.
Every time your completely drain your device, it kills your battery a little more each time. Avoid this by never letting your power run out entirely. If it can’t be avoided, you should preempt the forceful shutdown and turn the device off yourself. This will ultimately extend your gadget’s life.