Someone asked me what is mental strength. I believe it is a person's ability to continuously mobilize themselves to take action when facing real-world pressure, uncertainty, and long-term goals. It consists of four levels:

The first level, sense of meaning. Knowing why you are doing something. A sense of meaning determines direction.
The second level, emotional resilience. Being able to withstand anxiety, setbacks, misunderstandings, and failure without being overwhelmed by emotions.
The third level, attention. Being able to continuously focus limited mental resources on important matters rather than being constantly distracted by external factors.
The fourth level, willpower. Being able to keep taking action even without feedback, applause, or results.
A sense of meaning provides fuel, emotional resilience offers stability, attention provides focus, and willpower is responsible for the final execution.
Therefore: the body determines a person's physical limit, cognition determines a person's directional limit, and mental strength determines a person's endurance limit. Many people do not lose to ability, nor to opportunity, but in the long process of uncertainty, they exhaust their mental strength first.