A dying husband and his long-estranged wife wanted to reconnect. "The first two times that I saw them, they told the same memory five times," reports their therapist, Jefferson Singer, author of Memories that Matter: How to Use Self-Defining Memories to Understand and Change Your Life. Seventeen years before, they were driving home from the hospital where the husband had just been treated for alcoholism, a disease that wreaked havoc on their marriage. When his wife reached over to take his hand, he pulled it away, and she then pulled hers back. Since that moment, they had never been intimate.

During therapy, Singer encouraged them to set up their chairs as if they were back in that car, but in reversed roles. "Recreating this memory let them break through a wall and have empathy for each other." By retrospectively tampering with their script, the couple wrote themselves out of their emotional impasse.

The therapeutic power of memory can be especially great for older adults, whose early recollections take on a Technicolor-restored quality. A "life review" facilitated by a psychologist can generate insight, spur reconciliations and link disparate past eras. One study found that depressed seniors who practiced autobiographical memory retrieval for a month showed far fewer symptoms than a control group. The specificity of the memories they conjured could be the key to their mood boost: Depressed people recall much more vague memories than the nondepressed. But reevaluation of the past, not idle reminiscing, is what makes a life review beneficial.