The pace by which you develop as a chess player in terms of practical success (winning tournaments, increase in national and international rating points, making better decisions over the board) is most probably an individual thing. It is a complicated formula with many different components. But your character, your fighting spirit, will certainly be a key component of this formula.
Chess success happens over the board in the heat of combat. The nerves are on the edge and the classical time controls require a great deal of physical and mental energy. During a game you try to make plans, you try to direct play into areas where you have good know-how. But the game rarely follows the patterns that you anticipate, unexpected things can happen, you could make positional and material blunders, etc. Also, in cases you do get positional advantage, material advantage and/or attacking initiative, you still need to focus to keep the pressure and reach the ultimate goal of victory.
Fighting until the last drop, perhaps this sounds like a buzz phrase. But it is more than just advice. It is almost a philosophy, a path to development and success. Because those who use their energy moderately during a game and rarely go "all out" in terms of trying and fighting, they will probably reach results that correspond to the efforts made. You could fight an "equal" position to try to gain the initiative and win the game. You could keep playing in an "equal" position where you have virtually no risk of losing to see if you can find a win. You could keep playing every single game until bare kings. You could keep fighting even after you blundered or lost material to a tactical blow. The more of these things you do, the greater results you get.
After all. If the result is more important for you than for your opponent, you have the advantage in terms of fighting spirit. And that should count for something. Perhaps you often hear of the mistake of underestimating the opponent and losing because of this. What is underestimation? It is perhaps to lower your guard, to focus less, to feel comfortable in your chair, focusing becomes less important, perhaps winning in a convincing style becomes less important? Does this relate to fighting spirit? We think yes.
So. Pour your maximum energy and focus in every game. And how to use that energy? Well, that is what you should learn from books, videos and websites. But books cannot tell you how much energy to use in every game. They cannot give you a fighting spirit. This is probably an individual thing. This is probably up to you to find, bring and deliver at the board.