"I now no longer possess such an insolent spirit."
Not really his last words, but the last part of The Red Baron: The Fabled Ace's Story in His Own Words which is written in the first person. It is not clear exactly when it was written, but somewhere in these, his last months. It is easy to take this Thoughts in a Dugout essay as evidence that the Red Baron regretted the war or his role in it. But that doesn't fit the rest of the Red Baron's writings - or actions - very well. (Besides, anyone who makes room decor out of enemies' airplanes is not exactly showing standard pacifist sensitivities.)
Consider the context. This was a man with a head wound that probably counted as a traumatic brain injury, in a line of work that made many men "crack up," who had been in the war since it started, and had been under the pressure of being one of his nation's biggest celebrities, for more than a year, in a war that exhausted both nations and men. The whole essay could well fall under the heading of effects of traumatic brain injuries, which include "cognitive problems such as headache, difficulty thinking, memory problems, attention deficits, mood swings and frustration."
The writing sounds like the musings of other WWI aviators on both sides, who thought what they were doing was both a good thing and important, but who knew that civilians didn't understand it. (A common desire after a visit home seems to have been to return to the front where men really understood death, and life.)
Above But Not Beyond
Richthofen comments on why he doesn't quit flying, and perhaps that comment shows how he earned respect. He understands - as few celebrities do - that his life isn't any more precious than that of the average guy in the trenches.
Although Richthofen may feel that the war is no longer lively and merry, shortly after his death another man will start flying combat and earn fame in this war. Since they didn't overlap, it is this same part of the war that Richthofen feels has turned very serious and grim, which Rickenbacker will later look back on, commenting almost sadly that WWII pilots are much more serious than his own generation.
And now, the Red Baron...
Hanging from the ceiling in my dugout is a lamp I had made, as a conversation piece, from the engine of an airplane I shot down. I mounted small lamps in the cylinders, and when I lie awake at nights and let the light burn, Lord knows this chandelier looks fantastic and weird. When I lie that way, I have much to think about. I write this without knowing if anyone outside my closest relatives will ever see it. I am occupied with thoughts of continuing [his book] Der Rote Kampfflieger and, indeed, for quite a good reason. The battle now taking place on all Fronts has become awfully serious; there is nothing left of the "lively, merry war," as our deeds were called in the beginning. Now we must fight off despair and arm ourselves so that the enemy will not penetrate our country. I now have the gravest feeling that people have been exposed to quite another Richthofen than I really am. When I read my book, I smile at the insolence of it. I now no longer possess such an insolent spirit. It is not because I'm afraid, though one day death may be hard on my heels; no, it's not for that reason, although I think enough about it. One of my superiors advised me to give up flying, saying it will catch up with me one day. But I would become miserable if now, honored with glory and decorations, I became a pensioner of my own dignity in order to preserve my precious life for the nation while every poor fellow in the trenches endures his duty exactly as I did mine.
I am in wretched spirits after every aerial battle, but that no doubt is an aftereffect of my head wound. When I set foot on the ground again at my airfield after a flight, I go to my quarters and do not want to see anyone or hear anything. I think of this war as it really is, not as the people at home imagine, with a Hoorah! and a roar. It is very serious, very grim...