I do disagree with the idea that you are to expect hard contact in a semi contact sport sparring session as you need to learn how to take a knock for "the street" as some have suggested earlier. Semi contact free sparring is just that and has absolutely nothing to do with self defence.
If you are to be training and conditioning yourself for a hard knock for self defence purposes then that should be well explained to you first so that there are no surprises.
I was one of those who suggested that one of the benefits of sparring is that it teaches us to handle getting hit. I'm coming from a kenpo background, and that is the mindset in my art. I overlooked the possibility that a person could be training in TKD as a sport, rather than for SD purposes. No criticism was intended.