All of this is a reminder that fear is not the only way to motivate healthy behavior during a crisis. For much of the pandemic, the message from the C.D.C. has been one of “doom and gloom,” Dr. Jonathan Reiner of George Washington University told CNN. And fear can play an important role: Covid is a deadly disease, especially for people over 40. But fear tends to be effective “for only a short period of time, and then often engenders reactance and resistance,” Sarit Golub, a Hunter College psychology professor, has written. Hope can be more sustainable. As Reiner said, “When you give the public some positive reinforcement, it really can bear fruit.” In the case of the Covid vaccines, the hope is grounded in reality. Once you are fully vaccinated, you no longer need to organize your life around personal fear of Covid (unless you are immunocompromised). You can safely travel, eat in restaurants, shop in stores, visit with friends and hug your extended family. You can do all of it without a mask. Many other normal activities — like riding in a car or exposing yourself to a normal flu season — present more risk.