If you claim that every project or task is critical, your employees will soon ignore your sense of urgency and do things at their own pace (which is likely too slow for you). If everything is important or urgent, then nothing truly is. Use relativity to convey when a project is really critical to your organization or unit. Be selective about when you apply pressure or claim that something has high impact on your goals. The less often you raise alarm, the more likely your team is to respond how you want it to.