Sometimes sentence fragments are OK.

In school we were taught to write complete sentences. That is good advice, especially for new writers, but sentence fragments can work very well as part of a good writer’s style.

This use of a fragment works:
What was the effect of all that weeping? More weeping.

This use of fragments is overdone and therefore doesn’t work as well:
There was weeping. And more weeping. And more weeping.

This use of fragments seems like a mistake and, depending on context, probably is a mistake:
She wept and wept and wept. Because she could not stop weeping.