FLORHAM PARK, N.J. - As soon as the crowd dispersed, Sheldon Richardson quickly took a seat.

"My feet hurt. Gotta get used to running in cleats again," he said, smiling.

His month exile from playing football -- the result of a four-game suspension for failing a marijuana test -- has him a little rusty. But Richardson's return to the Jets (3-1) will provide a big boost to an already stout defensive line.

"I'm coming to eat, too," Richardson said of playing alongside Muhammad Wilkerson, Damon Harrison and rookie Leonard Williams. "No breaks for quarterbacks."

Richardson participated in a regular-season practice for the first time this season Monday and officially was added to the active roster after tight end Wes Saxton was waived.

On the heels of his announced suspension July 2, Richardson was arrested July 14 after an alleged high-speed chase with Missouri police. But as he sat in front of his locker Monday, dripping sweat, he vowed that he never will mess up again.

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"How do I know that?" he asked during a one-on-one interview with Newsday. "Just by every day; thinking about what I'm doing, how it will affect my family, my teammates, myself.

"It's been a rough year for me. Hardest year of my life. And I'm trying not to be this low again."

The Jets' 4-12 record in 2014 soured him, and the murder of a close family friend a month later shook Richardson to his core.

"He was with me. I dropped him off to his car and I went to his brother's house. And 30 minutes later, we got a phone call saying he wasn't there no more," Richardson said of his friend, Dorance Harvey, who was fatally shot in St. Louis on Jan. 30.

According to the St. Louis Post-Dispatch, Harvey, 23, suffered a gunshot wound to his neck and was pronounced dead at the scene. His car reportedly was chased by two dark-colored vehicles whose occupants fired "multiple shots." According to the newspaper, Harvey's car took "gunshot damage" and was still running and locked when it was found in front of a vacant lot. Richardson said the case still is pending.

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"I just wasn't used to losing somebody that close to me," he added.

Richardson had a hard time coping with the depression that followed. Nor did he grasp how reckless he was being July 14 when Missouri police clocked him driving his Bentley at 143 mph with a 12-year-old and a legally owned but loaded handgun in the car.

On Oct. 5, a Missouri judge postponed Richardson's hearing on charges relating to his arrest. He has pleaded not guilty to five misdemeanor charges, including resisting arrest.

Richardson -- who still could face additional punishment from the NFL -- said his absence from the team challenged him "mentally more than physically." But he said his twice-a-week meetings with the team psychologist, sometimes for "an hour or two, depending on the conversation," have helped.

"It started off a little different for me, as far as talking to someone about my problems. But other than that, it’s been easy," Richardson said. "[The doctor] is cool. I played him in chess. He didn't think I was capable of beating him. I beat him in 15 minutes."

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Asked what he's learned about himself through therapy, Richardson said: “I’m a dominant person. But I knew that already. He also said I was influential, believe it or not. He said I have the capability of choosing when I want to be influential or dominant. And he said I choose to be dominant. Stuff like that."

Richardson said that before the suspension and the arrest, "I really just didn't understand the meaning of [being a] public figure. I just love playing football and being able to support my family."

And he knows his friend, Harvey, would have had some choice words for him if he still were here.

"He probably would have said, with a smile: You're a fool," Richardson said. "Everybody close to me always says, you're representing a lot of people. You can be the person from St. Louis who actually does something and be a stepping-stone for other kids. And that's what I always wanted to be."