To "Die with your boots on" is an idiom referring to dying while fighting or to die while actively occupied/employed/working or in the middle of some action. A person who dies with their boots on keeps working to the end, as in "He’ll never quit—he’ll die with his boots on." The implication here is that they die while living their life as usual, and not of old age and being bedridden with illness, infirmity, etc.