In high school biology, we learn how we could take longitudinal sections and cross-sections. To slice a sliver of cucumber along its length would be to take a longitudinal section. To cut a circular chunk along its breath would be a cross-section.
Interventions can be longitudinal or cross-sectional. Deleting one’s Facebook account is a longitudinal intervention, while abstaining from using all social media on weekdays is to remove a distraction at the cross-section. To give up on eating cake is a longitudinal intervention, while abstaining from all desserts for 6 days a week is a cross-sectional decision.
It is often easier to cut something out at the cross-section than to single out and exclude a longitudinal slice. Just like it is with a cucumber.