Astronaut and retired U.S. Navy Captain Mark Kelly kicked off the 2013 International Roofing Expo with an inspiring speech about the lessons he learned during his 25-year career with the U.S. Navy and NASA. He also shared with attendees how he handled what he termed the greatest challenge in his life: the injury to his wife, U.S. Congresswoman Gabrielle Giffords.

Kelly reminisced about growing up in New Jersey with a mother who was training to become a police officer. He watched her every day training to pass the physical test in their backyard. She ended up exceeding her goal, beating most of the men in the process.

After seeing how hard his mom had worked to get that point, Kelly got a job and vowed to be more responsible.“That was the first time in my life I saw the power of having a goal and plan to achieve something,” said Kelly.

Kelly had always wanted to travel in space and dreamed about being the first person to walk on planet Mars. After detailing the hardships when landing his first naval flight, he said that “life is a set of challenges” and that you should have the practice, persistence and the drive to never give up.

Kelly realized the significance of communication during one of his flights over Iran. He said he experienced some life-changing moments that he will never forget, and said that there is never an excuse for not communicating with the people you work with. “Failing to communicate accurately and effectively nearly cost my life, and I have thought about it ever since.”

Kelly also stressed the importance of safety to contractors. “Always try to think about that first and reduce the risk.”

Kelly’s wife, Representative Gabrielle Giffords, was shot on Jan. 8, 2011, while speaking to constituents at an event near Tucson, Ariz. She was critically injured by a gunshot wound to the head; 13 other people were injured and six others were killed in the shooting. Giffords represented Arizona’s 8th congressional district from 2007 until her resignation on Jan. 25, 2012. “On January 8 2011, there was no countdown for me. I usually know when a combat mission is going to start with a countdown clock, but on that particular day there was no clock, just my phone ringing,” said Kelly.

Kelly shared his feelings about the day Gabby was shot. He was forced to watch the whole situation unfold on TV while waiting in the airport to fly out to Tucson. Throughout this whole experience, Kelly said he learned many life lessons from Gabby, including what it really means to be patient. He strives to be the exact same way with her.

Kelly went on to express his struggles with the decision to command the final flight of Space Shuttle Endeavor while Gabby was still recovering in the hospital.

He made his decision based on what Gabby would have wanted him to do. Since she is a big supporter of NASA and Kelly’s career, he decided to go forward with commanding the final flight. Gabby was able to be there for the final lift off of Space Shuttle Endeavour, but was unable to see Kelly land as she was in her final surgery.

“The power of the human spirit is incredible to experience,” said Kelly as he described how his wife handles her day-to-day struggles and never gives up.

Kelly ended his speech with a concluding quote from Gabby, who wished she could have been here but is working hard at her rehab and recovery. “Be passionate, be courageous, be strong and be your best.”