The worst thing that can happen when you first try to hack a device is its immunity, which is usually eliminated by a hard reset. Even complete file system corruption can be repaired with iTunes recovery. The only danger after a jailbreak is installing incompatible settings or downloading something unsafe.
Most versions of jailbreak include safe mode, which disables all your settings in case of incompatibility, so you can easily remove them and continue to use the device.
remember that you can always restore the firmware of your iOS device to factory default, this will fix any problem not related to the hardware. But keep in mind that this will result in the loss of the jailbreak until it is released for the updated version of iOS. All Jailbreak supported devices you can find here.
Can Jailbreak Destroy Your iPhone? - No. Jailbreak can't break your smartphone. If you want to install jailbreak, we can safely do it. Your iPhone won't get hurt. Most importantly, do not try to disassemble your iPhone and it will always be all right.