This quote is a profound commentary on the destructive power of negative influences and the loss of self that can occur when one succumbs to them. The character Hyde, in this context, represents the darker, more sinister aspects of human nature. To "cast in it with Hyde" is to align oneself with these negative traits, to let them take control. The result, as the quote suggests, is the death of "a thousand interests and aspirations." This means that by giving in to our darker side, we risk losing our passions, our goals, and our sense of purpose.

In today’s world, this idea is more relevant than ever. We live in an age where negative influences are rampant, whether it be in the form of harmful ideologies, toxic relationships, or self-destructive behaviors. Giving in to these influences can lead to a loss of personal identity and the abandonment of our dreams and ambitions.

In terms of personal development, this quote serves as a stark reminder of the importance of maintaining our integrity and staying true to our values, even in the face of temptation. It encourages us to resist the allure of the ‘Hyde’ within us and instead nurture the positive, constructive aspects of our personality. It suggests that by doing so, we can preserve our interests and aspirations, and ultimately lead a more fulfilling and meaningful life.