William Olson always saw his glass as half-full. Despite a childhood cancer diagnosis, he looked for ways to continue living.

“He had plenty to complain about, but that’s never what he did,” said Claire Olson, a sister who lives in Atlanta. “He wanted to find ways to make his life more enjoyable.”

Mr. Olson was first diagnosed with a malignant brain tumor in April 2001, when he was 14. From that moment on, he put all of his energy into getting better and enjoying life, said Nancy Olson, his mother who lives in Marietta.

“William always planned as if he were going to get well again, so that’s how we planned,” she said. “There were just some things he planned to do, that he won’t get to do.”

William Kolb Olson, of Marietta, died Wednesday at Piedmont Hospital, from complications of brain cancer. He was 25.

His body has been cremated and a memorial service is planned for 2 p.m. Saturday at Johnson Ferry Baptist Church. H.M. Patterson & Son, Canton Hill Chapel, is in charge of arrangements.

Mr. Olson grew up in Cobb County, attending Mt. Bethel Elementary and Dodgen Middle schools. His first relapse was in his junior year at Walton High School, in 2004, but he did not let his cancer diagnosis keep him from any of the major milestones teenagers look forward to, including getting a driver’s license and the prom.

“I remember the day he went to get his driver’s permit and he was sick as a dog, but he wanted to do it,” Mrs. Olson said. “I always operated on the premise that he was going to get better, and when he did I wanted to make sure we’d done everything we needed to so he could resume a normal life.”

Mr. Olson graduated from Walton High in 2005 and the next stop was college. He enrolled at Auburn, earned a degree in chemical engineering in May 2011, five months after he learned his cancer was back. He moved back home with his parents in December 2010 and started treatments again, but made it back to campus for graduation. By July, things were looking better, and by December he’d progressed from a wheelchair to a walker to a cane. By January 2012, he was driving himself around again, his mom said.

“And he got a job in mechanical engineering,” Mrs. Olson said. “It was just wonderful. He could work from home, or the office, and he was delighted.”

But in February, the tell-tell signs of tumor activity in the brain came back, his mom said. Though he was never able to regain his health, he retained his optimism and his sense of humor.

“He was really funny,” Ms. Olson said of her brother. “And sometimes he’d come with these one liners and you’d have to ask him if he was joking or serious, because what he said would be hysterical, but you couldn’t be sure he was joking.”

Mr. Olson’s zest for life gave the rest of his family strength, his sister said.

“His attitude made it easier for us,” she said. “Like someone told us the other day, William wasn’t afraid of dying, but he wasn’t ready to stop living.”

Mr. Olson is also survived by his father, Lee Olson, of Marietta; and grandparents, Bill and Marge Kolb of Dayton, Ohio.