Why did Jesus say that we needed to eat His flesh and drink His blood?

At first look it would be hard to justify this statement as it is.  However, the context of this discussion helps us understand what Jesus was meaning here.  Jesus had just fed the 5000 the day before and the people were looking for Him to do it again (John 6:26-27).  Jesus began to tell them that He was the bread from Heaven, and unlike the manna of Moses, He could grant them everlasting life (John 6:35).  Jesus then famously told them that they must eat His flesh and drink His blood to inherit everlasting life (John 6:54).  A few verses later Jesus explains that this is spiritual and not physical, meaning that we need to allow Jesus to fill our entire being and then we will be saved (John 6:63).  However even with this explanation, it was a hard saying then, and it is a hard saying now (John 6:60).