You actually can't really cancel it the way you've built it. So, every lead that has ever flowed through the campaign earlier is in a wait step. Even if you were to never run this campaign again, those leads would continue to make their way through it.
The recurring part of the campaign starts new leads at the top of the process, which they'll work their way through. You'll have leads at various stages of the flow, so editing a wait step probably isn't a good idea either as people will be in multiple places.
This sort of thing is why we built the new Engagement Module, so people could eaisly pause the flow.