Sean Hayes has writer's cramp.

"I'm signing individual, personalized goodbyes to close to 300 people on the show. It's great to give my hand a rest," the 35-year-old Emmy winner says from his office at Hazy Mills Productions, the company he runs with longtime friend and business partner Todd Milliner.

It's just a few days before Hayes will go before TV cameras for the last time as Jack McFarland, the manic, flamboyantly gay character who turned the Chicago-born actor into an overnight star when "Will & Grace" premiered in 1998. The NBC sitcom ends its eight-season run with a special hourlong finale on Thursday, May 18, preceded by an one-hour retrospective.

"I can tell you that it's funny and, as in the pilot, the episode is about the characters Will and Grace, with the characters of Jack and Karen there to support the Will and Grace story -- which I think is the way to end the show," Hayes says of the wrapped-in-secrecy finale. "Jack and Karen don't need these incredible loose ends to be tied up, although we'll give the fans some kind of closure for them as well."

Obviously, the episode offers personal closure as well for Hayes, who confesses to mixed feelings as he leaves his most successful gig to date.

"It's bittersweet, actually," he says. "I got the show when I was 27 years old, and I had no experience in sitcoms and very little in TV at all. It was a tidal wave of emotion, a life-changing experience, when I got the show.

"I never really pounded the pavement for a job in Los Angeles, and I know some people hate me for that, because I got lucky so quick. I could understand the animosity other actors felt when I was that age.

"I had done 30 or 40 commercials, but the point I'm getting to is that, as sad as I am to leave, to not be able to see these people every day, I'm looking forward to other experiences in life that I haven't had the opportunity to seek out yet."

A breakout star from the moment "Will & Grace" hit the airwaves, Hayes was passed over for an Emmy nomination as best supporting comedy actor after the show's first season but got an even more meaningful pat on the back when the winner, David Hyde Pierce of "Frasier," used his own Emmy acceptance speech to gently chide the voters for overlooking Hayes' performance.

It was a gracious gesture that Hayes still cherishes.

"That was an unbelievable moment in my life," he says quietly. "Totally surreal. I was sitting on my couch, in my sweats and T-shirt, watching the Emmys by myself, and then he said my name and this wave of heat came to my face. At first it was like an out-of-body experience, where I thought, 'How nice that he said that guy's name,' and it took a minute to sink in that he was talking about me. I sent him these huge flowers afterwards. What a selfless, kind and incredibly generous thing for him to say!"

Perceptive, too, because Hayes found himself at the award podium during the 2000 ceremonies, when he won an Emmy of his own. He has been nominated every season since, in addition to receiving multiple other awards and nominations.

With success like this, another actor might be feeling pretty cocky as he leaves for what should be greener pastures.

Not Hayes, who confesses to chronic insecurity when it comes to finances.

"If you knew me better, you'd realize I never relax about money. I'm constantly nervous, thinking I'm going to be poor again tomorrow," he says. "You go one winter without heat in Chicago, and it changes your life. You just don't forget that. My father left us early on, and my mom raised five kids by herself. In addition to no heat, our car was repossessed and the phone was turned off. After something like that, the second you become financially successful, you do everything you can think of to protect it, because the fear is just that large.

"I know that I will always, always, always worry about where my next job will come from -- which makes me work harder. That's why I started a production company, and we have TV shows and films in development."

Off-camera, Hayes is warm and friendly but much, much lower-key than his frenetic "Will & Grace" alter ego, a fame junkie who kept reviving his appalling one-man theater piece, "Just Jack." In fact, Hayes insists he is walking away from this long-running hit pretty much the same person he was when he landed the job eight years ago.

"Every actor brings a part of himself to a role, so clearly there is a part of Jack inside me, but my God, I would be exhausted to live that character 24 hours a day," he says.

"I have the same friends that I've always had, and obviously the same family. I have the same work ethic. Because it happened so early for me and so quickly, I have set my mind to enter that same space as where I was before I got 'Will & Grace.' I'm trying to psych myself into believing that only five minutes have passed, not eight years, and now let's roll up our sleeves and start working. That's kind of how I'm attacking the next phase of my life."