Unfortunately, Hemingway wasn't able to use this attitude in his real life. Maybe the pressure simply was to high. The general public did never know the real Ernest Hemingway, who was a human with a human's problems. They only had an abstract ideal they knew from his books, even his close friend James Joyce mixed him up with his characters. Cited verbatim: He's a good writer, Hemingway. He writes as he is. He's a big, powerful peasant, as strong as a buffalo. A sportsman. And ready to live the life he writes about. He would never have it if his body had not allowed him to live it. But giants of his sort are truly modest; there is much more behind Hemingway's form than people know. (Burgess (9.), p. 39)
According to Ford Madox Ford truth was not facts but vision, that is the principle Hemingway's characters are based on and that is what caused Hemingway's failure. He was forced to try and achieve the same straightness and stoicism his characters had. The difference was just that he was a real person, and they were, like Kundera's characters, born of an idea and existed just in fiction.
Like Robert Jordan's father, he was trapped. On the one hand, he could never surpass his character's deeds and on the other hand, the general public demanded him to do so. He tried and created one myth after the other. He claimed he had an affair with Mata Hari ("but one night I fucked her very well, although I found her to be very heavy throughout the hips and to have more desire for what was done to her than what she was giving to the man"(Burgess (9.), p. 105)), that he joined the Arditi after his wounding, etc. And most people were perfectly willing to believe it, the tale about the Arditi, Italian shock troops, even appeared in Malcolm Cowley's preface to the 1944(Cowley (4.), p. xii) edition of "The Viking Portable Library". He was captured in the structure of his lies, the discrepancy between him and the image he had set up grew larger every day. To be a liar and worthless in comparison to that shining idol must have reinforced his alcohol-related depressions and made him more liable to the hurts he received.
After all, there is a certain ambivalence of death and violence. It had done some good, it taught him priceless philosophies, but at the same time, it hurt him so much, that they were useless to him. The only thing he could do was to fictionalize them.