S.W.
I'm not a "tough love" parent until I've exhausted all other options. Children can and do suffer from real anxiety. It can come on due to some traumatic event, or due to nothing at all. I would want to investigate that possibility, through a pediatrician and counselor, before treating this as a discipline need. It's not normal behavior, in my experience, at this age, so I would be looking for a cause before deciding on a treatment.