For whatever reason, I always find this kind of thing reassuring. I frequently feel like there's a great deal more that I want to read and understand and write and do, and thus it's encouraging to hear that there's still time. Indeed, that it is unusual, in life, for people to already have their major accomplishments behind them by their forties.
Similarly, whenever I start to let myself get too frustrated about things at work, I recall an article I read a number of years ago which said that years of highest earnings in a man's career are from ages 50 to 55.
Foote himself was something of a late bloomer as a historian, starting his Narrative in his late 30s. The first volume was published when he was 42, and the last when he was 58. And the series did not reach its peak of popularity until he was in his early 70s, when he featured in Ken Burns' Civil War documentaries. Reading a little about Foote, I was particularly amused by this anecdote:
Foote labored to maintain his objectivity in the narrative despite his Southern upbringing. He deliberately avoided Lost Cause mythologizing in his work. He gained immense respect for such disparate figures as Ulysses Grant, William T. Sherman, Patrick Cleburne, and Edwin Stanton. He grew to despise such figures as Phil Sheridan and Joe Johnston. He considered United States President Abraham Lincoln and Confederate General Nathan Bedford Forrest to be two authentic geniuses of the war. He stated this opinion once in conversation with one of General Forrest's granddaughters. She replied, after a pause, "You know, we never thought much of Mr. Lincoln in my family."