I don't think your lack of tears are anything to be concerned about. The process of writing can be incredibly emotional and even cathartic at times, but everyone reacts differently. And while I'm sure it's true that Rowling sobbed at the end, it's also a great emotional hook to stoke the fire right before the last book comes out. Certainly sounds better than if she had said "I wrote the end then went and had some tea and toast and watched the telly."