Salt craving........?

I've never much cared for salt. I rarely use it when I cook and never salt my food additionally. Recently, i've been on a cardiac diet and have limited my whole sodium intake. Today, i've had the worst craving for salt. So much that I actually added salt to my lunch and it tasted good (again, I hate salt). I was just wondering if a person's body can have a sodium deficiency? Is there a certain amount of sodium that a person SHOULD have everyday?