sink or swim

If you are left in a situation where you must sink or swim, it means that you are not given any sort of help or support in this situation and you must help yourself. To sink or swim is another way to say that it is entirely up to you whether you fail or succeed at something in regards to this particular situation. This is often used figuratively as a way to say that people wont always be there to help you and you have to learn how to help yourself.