David Letterman has opened up about his retirement, telling his hometown's Indianapolis Monthly magazine that he goes trout fishing with his son Harry and adding, apparently jokingly, that "As it turns out, after all these years of having someone make my calls for me, I can no longer operate a telephone." The former "Late Show with David Letterman" host, 68, told college friend Ron Pearson he's retained two of his assistants from the CBS program. "It's stunning what you find out about yourself when everything you've done for 33 years changes. It's like ice melting out from under you. I know that regular, responsible people probably hear me whining like this and think, 'Oh, brother.' "