(CNN) -- Tony Stewart says he took the last three weekends off to respect the family of the driver that his race car struck and killed this month, and to deal with his own emotions.
Returning to NASCAR racing this weekend, he says, will help him cope.
Stewart, who opted out of three races after his car hit Kevin Ward Jr. during a dirt track race on August 9, spoke briefly to reporters Friday about his decision to race in Sunday's Oral-B USA 500 at the Atlanta Motor Speedway.
"This has been one of the toughest tragedies I've ever had to deal with, both professionally and personally. And this is something that will definitely affect my life forever," Stewart said at the speedway in his first public appearance since Ward's death.
While the incident hit him hard, Stewart said he knows "that the pain and the mourning that Kevin Ward's family and friends are experiencing is something that I can't possibly imagine."
"(The time off) has given me the time to think about life and how easy it is to take it for granted," Stewart said. "I miss my team, my teammates, and I miss being back in the race car. I think that being back in the car this week with my racing family will help me get through this difficult time."
He declined to take reporters' questions, saying he needed to respect the investigation into Ward's death.
New York authorities continue to investigate the incident, which happened after Ward crashed and then exited his race car during an Empire Super Sprints series race in New York.
Spectator video from that night at the Canandaigua Motorsports Park race shows two cars coming out of a turn, with Stewart's No. 14 car sliding up the track toward Ward's No. 13 car. The two cars get close and appear to make contact before Ward's car hits the wall and spins out.
Ward gets out of his crashed car and walks determinedly on the track toward the race cars, which had slowed for a yellow flag. Ward points a finger and appears to be yelling. One car swerves to avoid Ward on the half-mile dirt track.
Stewart's car passes close to Ward, and it appears that its right rear tire hits him. Authorities said that the 20-year-old Ward, a New York sprint car driver, died of "massive blunt trauma."
Stewart withdrew from the NASCAR race in New York's Watkins Glen the day after Ward died. He also missed races in Michigan and Tennessee.
Ontario County Sheriff Philip C. Povero said at the time that there was no evidence that a crime had been committed.
Stewart said that he wants Ward's parents and sisters "to know that every day I'm thinking about them and praying for them."
Ward, from Port Leyden, New York, was in his fifth season in the Empire Super Sprints series. He began racing when he was 4, running go-kart events. When he was 12, he moved to the faster sprint cars.
His father blames Stewart for hitting his son.
"Apparently, Tony Stewart was the only one driving out there who didn't see him," the father said, according to Syracuse.com.
Brett Frood, executive vice president of Stewart's racing team, Stewart-Hass, said Friday that Stewart sent the Ward family flowers and a card, and that eventually he will want to spend time with them
"I do believe that will happen at the appropriate time," Frood said.
Meanwhile, Stewart will be eligible for this year's "Chase for the NASCAR Sprint Cup" playoff system if he wins either in Atlanta or next week in Richmond -- the last two races of the regular season -- NASCAR President Mike Helton said.
There had been speculation that Stewart would have been ineligible because he missed the last three races. NASCAR had said previously that to qualify, a driver must attempt to qualify for all 26 races leading up to the Chase.
But Helton said Friday that NASCAR was waiving that requirement because of the "unique set of circumstances" in this case.
CNN's Wayne Sterling contributed to this report.