For all of the skills that astronaut and United States Navy Capt. Mark Kelly learned in the air, some of his biggest life lessons were learned on the ground.

Through his mother, who became one of New Jersey 's first female police officers, and his wife, former United States congresswoman Gabrielle "Gabby' Giffords, Kelly said he 's been taught the value of hard work, perseverance and passion.

Kelly, who spoke Tuesday at the University of Texas at Arlington 's Maverick Speakers Series, said despite his military combat missions and four space shuttle voyages, his work proved not as life-threatening as his wife 's. Giffords was shot in the head at an Arizona meeting with constituents on January 8, 2011, in which six others were killed and 12 were injured.

"Most people don 't survive that kind of injury. And if they do, they 're severely disabled,' he said of Giffords, who, through multiple surgeries and extensive rehabilitation, not only survived the attack but returned to Washington D.C. for a pivotal vote and watched his final shuttle launch.

"I 've never been so proud of someone in my entire life,' he said.

Giffords, who resigned her congressional seat, and Kelly, who retired from NASA, have emerged as gun control advocates and have placed themselves in the center of the national debate over the issue. Recently, they launched Americans for Responsible Solutions, which calls for criminal background checks and limiting assault weapons and high-capacity magazines.

Kelly said he and his family 's lives forever were changed that day in Tucson two years ago. Becoming a primary care giver, he said, required he learn a new skill set, one that was foreign for the pilot accustomed to speed.

"Progress was painfully slow,' he said. "I 've never thought of myself as a patient person.'

Today, Giffords undergoes regular speech, physical and occupational therapy, and she teaches him daily the strength of the human spirit, Kelly said.

"The man who shot Gabby may have put a bullet in her head, but he didn 't put a dent in her spirit,' he said. Kelly told the crowd that his wife sent her wishes, which he read from a note in his pocket. " 'Be passionate. Be courageous. Be strong. Be your best. ''

Looking back on his career, Kelly, who spent a total of 55 days in space over his four shuttle missions, acknowledged the risk in space flight. He described a shuttle launch feeling like "the hand of God came down' and yanked him from the ground and the act of bringing a shuttle back to earth as "a series of minor miracles.'

To balance those risks, he touted communication and attention to detail, which he noted are important in life as well.

During a Q&A at the end of his speech, he told UTA students that making good grades and being driven is important, but being persistent matters, too.

"I really do believe that how good you are at something in the beginning is not an indication of how good you can become,' he said.