When there is something pleasant that one doesn't want to indulge in, like junk food or alcohol, the key to avoiding temptation is to interrupt the habitual response with a quick, easy alternative action, says Dr. Gollwitzer.

WSJ: Resolutions: So Irresistible, So Hard to Keep

"Most people are having a lot of flashbacks, " and thoughts of the bombing interrupt their days and nights, said Lisa Allee, who directs the Community Violence Response Team at Boston Medical Center.

NPR: Anger, Fear, Tears Normal Response To Disasters