At work, you have to remind yourself that not everything is resting completely on your shoulders -- stop putting so much pressure on yourself, because no one else is. Coworkers are there for a reason. They're not only there to do their job, but to fulfill their roles in the team. So if you need them to step it up a bit, then you should feel free to ask them to. Just do it face-to-face. An email won't convey the right tone, and could ruffle their feathers.