Last February, I vowed to go the whole month without using sarcasm. The challenge left me practically speechless. I blame David Letterman. But mostly, I credit him.

I was 12 when I discovered Letterman. I've spent nearly a quarter-century with my late-night hero. And over that time, I've learned to be a smartass with a heart, just like Dave.

Growing up, I mimicked the Letterman one-liner, his slow-burn reactions, and his habit of beating jokes into the ground. I repeated Dave's wisecracks so often ("There is no off position on the genius switch"), that soon his jokes became mine. Even today, I am often stunned to hear Dave tell jokes that for years I thought I had conceived.

Dave's door-to-door romps through the New Jersey suburbs were the inspiration for the well-intentioned mischief-making of my teenage pals and I in the late '90s. We swarmed the streets of suburban San Diego County armed with clunky camcorders and clipboards filled with provocative questions to ask random people on the street, helpless pharmacists stuck behind counters, and perplexed purveyors of tuxedo shops. We went into a Vons, bought toilet paper, and then TP-ed the outside of the grocery store. We serenaded the late-night cooks at a dingy taco shop with "You've Lost That Lovin' Feeling." We were silly and sarcastic and drunk on the fun of it all (without actually being drunk, I might add). We edited our videos on a couple of VCRs and mastered Dave's signature cutaway shot to the dumbfounded stranger confused by our antics. We had a blast.

I was the most obsessed among us. I sported a Late Show varsity jacket to junior high and took pride in my own gap-toothed smile. My rabbit was named Shaffer for the bandleader, and — even though it was a continent away — I made regular pilgrimages to the Ed Sullivan Theater just to stare at its marquee.

But here's the thing about my fascination with Dave: It's not because I'm a comedian, or even because I ever really wanted to be one. When it comes to career, I'm a somewhat serious person who has always wanted to "make a difference" — and that's something I knew even as a teenaged Letterman super fan. Over the last decade, I've worked in politics (on the ill-fated Howard Dean campaign in 2004), journalism (at several newspapers around the country), and the law. Today, I'm an attorney in Seattle who prosecutes domestic violence perpetrators.

Dave inspired countless stand-ups and comic performers. (For the most moving tribute, fast-forward to the six-minute mark of Norm Macdonald's appearance on Friday's Late Show.) Dave also endeared millions upon millions of non-comedian Americans, across geography and generations, who chuckled along with him, first on NBC's Late Night, then on CBS's Late Show. But I don't fit neatly into either category. I was more than a regular viewer. But I also never saw myself growing up and becoming a stand-up. Instead, I wanted to be like Letterman without actually being Letterman. And I think that's happened — as evidenced by my near-inability to speak without sarcasm for a month.

I was always awed not only by Dave's razor-sharp wit and bowl-you-over intellect, but by his Indiana kindness and ability to find what is beautiful and great and hilarious in a camera-shy stage manager or stiff-talking deli owner. He was sarcastic without being cruel, hilarious without being crude. He was impossible not to like and laugh with. He was exactly the kind of guy I wanted to be.

It was outside the Ed Sullivan Theater that I finally met Dave, when I was 15. Late one night, I stood on a deserted sidewalk outside the stage door shivering in a snowstorm. My long-suffering mother looked on through the frosted windows of an all-night Dunkin Donuts across Broadway.

As I clutched a Late Show hat for him to sign and rehearsed what I would say, I couldn't help worrying, was I about to be let down? What if the famously prickly comedian blew me off? Could I survive rejection by this man I idolized?

At about 10 p.m., I watched as a red sports car slowly rolled up the empty street and stopped at the stage door. A young assistant got out and left the engine running, oblivious to the frozen kid loitering in the dark. The stage door swung open and out walked David Letterman, in flesh and blood, hustling through the sleet toward the warmth of his car. Just before he got in, I summoned the nerve.

"Excuse me, Dave? I just wanted to meet you." Perhaps startled to hear a voice, Dave slowly turned around. He eyed me, smiled, and extended a hand.

"Hi, how do you do?" said Dave, his ball cap pulled low above his glasses.

I dove in with my prepared remarks about my admiration for him. Dave patiently listened and then turned the conversation to me, asking my age and where I was from.

I then asked Dave to sign my hat, and he obliged, taking it in his hands. For an awkward moment, we stood there shivering in the cold. Dave stared at me expectantly, and I stared back, until I realized — oh crap, I don't have a pen. Somehow this one detail never crossed my mind.

"Um, do you have a pen?" I asked. Dave smiled wryly. "No, I'm sorry, I don't." With that, he wished me good night, stepped into his car, and slowly navigated down West 53rd Street.

In the end, I settled for an autographed promotional photo of Dave holding a baseball bat that his show sent me. The same photo surely hung in the bedrooms of countless other teenaged misfits who perhaps saw a little of themselves in Dave.

This week, as the Late Show goes dark, and my hero retires, Adam Sandler's recent words lamenting the loss of the host ring true for me as well: I'm losing my best friend on TV.

As he exits the stage, I'm left with that autographed photo packed up somewhere with my videotapes and Late Show jacket, along with my memory of Dave and lingering on the sidewalk until his car disappeared into the city. But more than anything, what Dave really gave me will never leave me. Because it's me — it's who I am.