If you happen to run into Aaron Paul these days, you’re likely to encounter an actor almost bursting with warmth and bliss — in other words, the polar opposite of Jesse Pinkman, the tortured junkie Paul plays on AMC’s"Breaking Bad.”

The Emmy winner has many reasons behind his positive vibe: He’s “madly in love” with his fiancée whom he plans to marry next year and he’s enjoying a few months off from filming the series.

Despite the good mood, Paul is preparing for the emotional storm clouds on the horizon: “Breaking Bad,” which has established Paul as one of Hollywood’s most vivid young talents, is launching its fifth and final season Sunday, and will end its run next year.

PHOTOS: Celebrity portraits by the Times

“I know I’m going to be a mess, a sobbing mess,” Paul said last week in an interview at the Chateau Marmont, just a stone’s throw from his West Hollywood home. “I’m going to miss it horribly.”

The pain will be postponed slightly because the 16-episode final season of “Breaking Bad” — one of AMC’s flagship shows, along with"Mad Men"and"The Walking Dead"— is being divided in half, with the concluding eight installments airing next summer.

Almost a year before that finale airs, Paul said the mood on the set in Albuquerque, N.M., is noticeably different this season for the cast: “It’s the first time where we can see the finish line, and it’s really bittersweet. Each of us is coming up with all these crazy theories about how each one of us is going to die. ‘Breaking Bad’ is just one of those shows where you never know who is going to survive and who’s not going to survive.”

PHOTOS: TV villains we love to hate

He added, “I think it’s going to end in a very honest way. We’ve got to end this right, and it’s going to end very violently, which is what our fans want.” He leaned forward in his chair and flashed a mischievous smile: “Isn’t that what you want?”

No matter who is left standing at the end, Paul will miss being swallowed up in his character’s relentless turmoil: “I will miss not being able to zip on Jesse’s skin for a few more years.”

“Zipping on that skin” means confronting an avalanche of inner and outer demons that have made Jesse one of the most cursed and troubled characters in prime time. An edgy, uneducated drug addict who has alienated his family and almost everyone close to him, Jesse is also neck-deep in a perilous criminal enterprise that continually puts him in harm’s way. He’s committed murder, suffered nervous breakdowns, taken brutal beatings and has dodged death several times.

WATCH: Aaron Paul, Jon Hamm and Michael C. Hall talk drama

Playing Jesse has required Paul to venture into his own dark places. “I have to be alone to prepare. For the more dramatic scenes, I’ve been alone and weeping, trying to get into that mind-set. I feel for Jesse and I want to protect him.”

Protecting Jesse has its own peril: The character’s greatest threat unknowingly comes from Walter White (Bryan Cranston), his closest ally and partner in crime. Walter, the former chemistry teacher who has transformed into a ruthless gangster, was instrumental in the drug overdose death of his beloved girlfriend Jane, and poisoned a young boy Jesse adored, framing his rival Gus Fring (Giancarlo Esposito) as culprit to win Jesse’s support in knocking off Gus. Jesse has no idea of his partner’s involvement in those tragedies, and his possible discovery could play a major part in the show’s conclusion.

Ironically, the twists and turns over the last four seasons that have defined Jesse’s evolution also placed him closer to the drama’s central core, originally solely occupied by Walter. With Walter increasingly unsympathetic and violent, Jesse — murderer, addict, bottom-feeder — gradually became the conscience of the series.

That transformation is even more surprising with the revelation that Jesse was not supposed to survive the first season.

“In the beginning I had no idea how important Jesse was to the series,” said the show’s creator and executive producer, Vince Gilligan. “He was a bit disposable at one time. But Aaron brought such artistry and hope and humor to the character. The series is supposed to be about Walter White, but I realize that the show is fast becoming a two-hander. Jesse represents the heart of ‘Breaking Bad.’”

Added Cranston: “When I first met Aaron, he seemed like the perfect foil. He was a lot like Jesse in many ways — vulnerable and sensitive. But he’s brought this empowerment to this character. He’s a drug abuser, he doesn’t care about education, he gets very far with his ignorance, but yet you feel for him. That’s a true tribute to Aaron.”

Though Paul wears his hair close-cropped like Jesse, he said he is nothing like his on-screen alter ego: “We’re at completely opposite ends of the spectrum. But Jesse has a good heart, and I like to think I do. And I know what he feels. At a certain point in my life, I was also this lost kid trying to find my way.”

Paul grew up in a small Idaho town with an extremely religious Southern Baptist family. “I knew I wanted to be an actor at a very young age,” he said. “I was just obsessed with TV and movies, and I didn’t know how to go about getting into the industry. I graduated high school early and moved out to L.A. when I was 17. I thought ‘the world is my oyster,’ but I was still very much an infant.” Watching those around him, Paul said, “I saw a lot of people have success handed to them that then exploited it. They didn’t protect it or cherish it.”

His early career included the MTV film “Wasted,” a video for the group Korn and films such as “K-Pax” and “The Last House on the Left.” His most prominent part before “Breaking Bad was as Scott Quittman, the boyfriend and eventual husband of Sara (Amanda Seyfried) on"Big Love.”

“I’m a character actor,” he said. “I’m not a leading man. I love playing odd roles.”

He’s taking on another intense role in the upcoming independent film “Smashed,"as an alcoholic married to another alcoholic (Mary Elizabeth Winstead). But it’s “Breaking Bad” that he is centered on for the moment. Though he has no clue what the end will bring, he assures fans it will be explosive.

“I can’t imagine this show having a ‘Brady Bunch’ ending,” Paul said, smiling. “I do know it will be a mess.”

greg.braxton@latimes.com

PHOTOS, VIDEO AND MORE: