If doing the work is causing stress and detracting from EC’s I would do the WP. But a B is fine on your transcript so if the grade is stressing you rather than the workload, stay in the class.
We can’t really tell from your post what the source of stress is: the workload, the impact on EC’s, or the grade. My response depends on the source of stress. No matter what course of action you take, I think you will be fine.