Definition
This phrase is used to warn someone that they will be solely responsible for the outcome of their actions.
责任自负
If you insist on driving in that weather, on your own head be it if anything happens.
如果你坚持在那种天气下开车，如果发生任何事情，后果自负。
I know you're eager to try it, but on your own head be it if the plan fails.
我知道你很想尝试，但如果计划失败，后果自负。
They've warned you, but you've decided to do it anyway, so on your own head be it.
他们已经警告过你了，但你还是决定要做，所以后果自负。