There is a hole in the heart of Missouri with the passing of former Sen. Tom Eagleton (D). He was a giant among leaders and leaves a legacy that should guide public servants for generations to come.

Beginning in 1956 at the age of 27, Tom Eagleton took the world by storm with his wild ambition. In a brief 12-year span, his political career launched him to the positions of state attorney general, lieutenant governor and Senator. In 1968 when Missourians sent our “boy wonder” to Washington, we knew he would achieve greatness. And he did.

Within his first term he had already begun to turn the tide on the environmental damage that ensued in the half-century after the industrial revolution by crafting and enacting the Clean Air Act of 1970 and the Clean Water Act of 1972. He established the Pell Grant higher education assistance program, was an advocate for children with disabilities and created the National Institute on Aging.

While much of what Tom Eagleton did in the Senate made a true impact on America and the world, no action may have been as great as his handwritten amendment that stopped the bombing in Cambodia. This courageous act changed the course of history by subsequently ending the Vietnam War. His complete grasp of the complexities of foreign policy continued until his death. He was an early and thoughtful critic of the Iraq War because of his deep understanding of the region and its people.

Despite the fact that Tom Eagleton was a scholar at Amherst College in Massachusetts and Oxford and a cum laude graduate from Harvard Law School, as well as a Navy sailor and son of a prominent St. Louis attorney and politician, he could relate to almost anyone.

“Just call me Tom,” he would say with a warm grin and a firm handshake. That was his style: plain-spoken, genuine and usually the funniest man in the room.

His ability to be the voice of everyday Americans was the reason he was elected to three terms in the Senate and the same reason it was so hard for him to leave public service in 1986.

He left office with the most modest of words, saying, “There is no sadness in leaving public life while you still have something worthwhile to do and the time and motivation to do it.”

In the famous style and personality that was Tom Eagleton, he was gone from public office but not from public life. A university lecturer, political commentator, philanthropic fundraiser, community advocate and sports enthusiast, Tom continued to pursue dreams of a different kind.

While Tom shied away from claiming due credit, his good friend and colleague from the other side of the aisle, Sen. John Danforth, summed up his amazing political career by saying, “What has set Tom Eagleton apart from the rest of us is not his intellect and his energy, impressive as they are. It is his moral passion, his capacity for outrage, his insistence that justice be done, that wrongs be made right.”

More than what Americans gained from his victories, achievements, degrees and accolades, it’s the lessons we find in his words that we can take with us into the future. Be civil and modest. Act with courage and integrity. Pursue your dreams and do right by your neighbors. And most of all, don’t take yourself too seriously.

Sen. Claire McCaskill is a Democrat from Missouri.