This quote by Leonardo da Vinci is essentially about self-mastery and the power of the mind. In saying that a great man "presides over all his states of consciousness with obstinate rigor," da Vinci is suggesting that a truly exceptional individual is one who has complete control over his thoughts, emotions, and perceptions. This control is not easily won, as indicated by the term "obstinate rigor," which suggests a determined, unwavering effort.

The "states of consciousness" that da Vinci refers to could be interpreted as the various mental and emotional states we experience, such as joy, sadness, anger, fear, curiosity, and so on. To preside over these states implies a high level of self-awareness, as well as the ability to choose one’s response rather than simply reacting to external circumstances.

In today’s world, this idea is highly relevant in the context of emotional intelligence and personal development. Many modern psychologists and personal development coaches emphasize the importance of self-awareness and emotional regulation, both of which align with da Vinci’s concept of presiding over one’s states of consciousness.

For instance, instead of allowing a negative event to ruin your day, you could choose to acknowledge your initial feelings of frustration or disappointment and then consciously shift your focus to something more positive or constructive. This doesn’t mean suppressing or ignoring negative emotions, but rather acknowledging them and then making a conscious decision not to let them control your behavior or state of mind.

In personal development, this quote could be a powerful reminder that we have more control over our internal states than we often realize. It encourages us to strive for self-mastery, to cultivate self-awareness, and to take responsibility for our own mental and emotional well-being. It suggests that greatness is not necessarily about external achievements, but rather about the ability to manage our own minds with "obstinate rigor.