Nagase Takuya is a player of Japanese chess. He is one of the most competent players now. One day he said as below in an interview. (I cite it after removing a question by an interviewer.)
It is to breathe or to live for me to make an effort. It is just a habit, so it doesn't need the force of will.
On the other hand, I think to show 'guts' is to hold out forcibly. It makes us too much tense and increases our mental damage if we fail. However, we need guts when we want to achieve a result in a short period. I wonder if 'effort' is the antonym of 'guts' rather than the synonym.
Fujii Takeshi is a player of Japanese chess. Many fans respect him because he has pursued Shikenbisha throughout his career. Shikenbisha is one of the strategies of Japanese chess, and Fujii loves it. At the end of the ’90s, he invented a crucially unique approach that reconstructed the standard of Shikenbisha. This approach was named the Fujii System after him.
Let's read a part of the note that expresses his spirit well.
I have determined that I never lose the do-or-die game since I was a teenager. Although my playing style and thought have changed entirely, this determination is unchanging.
Of course, the world of Japanese chess is severe. No one can win just because of a resolution. I think, however, a player who doesn't have a resolution can't survive in this world. We should have a decision to win; nevertheless, it is vague and impudent at first.
Self-confidence enables us to make a decision. Then, what gives us confidence? Nothing gives it to us. Each player must believe oneself by oneself. I learned this law while I was struggling to be a professional player.
I will continue my pursuit with self-confidence, till the moment I leave the stage of professional.