Here's another answer: The "for the want of nail..." proverb, which is somewhat related to FX_'s answer, the Butterfly Effect, in that both proverbs emphasize the power of insignificant things to cause momentous changes further on. However, in my observation, the Butterfly Effect is mostly referenced neutrally, and a few times even positively, say for example when describing the power of small act of kindness to enable the performer to reap larger "karmic" rewards later. On the other hand, the "for the want of the nail..." story usually has uniformly negative connotations, in emphasizing the role of unpreparedness in causing momentous tragedies in ventures of a complex nature.

Here's another answer: The "for the want of nail..." proverb, which is somewhat related to FX_'s answer, the Butterfly Effect, in that both proverbs emphasize the power of insignificant things to cause momentous changes further on. However, in my observation, the Butterfly Effect is mostly referenced neutrally, and a few times even positively, say for example when describing the power of small act of kindness to enable the performer to reap larger "karmic" rewards later. On the other hand, the "for the want of the nail..." story usually has uniformly negative connotations, in emphasizing the role of unpreparedness in causing momentous tragedies in ventures of a complex nature.

Here's another answer: The "for the want of nail..." proverb, which is somewhat related to FX_'s answer, the Butterfly Effect, in that both proverbs emphasize the power of insignificant things to cause momentous changes further on. However, in my observation, the Butterfly Effect is mostly referenced neutrally, and a few times even positively, say for example when describing the power of small act of kindness to enable the performer to reap larger "karmic" rewards later. On the other hand, the "for the want of the nail..." story usually has uniformly negative connotations, in emphasizing the role of unpreparedness in causing momentous tragedies in ventures of a complex nature.

Here's another answer: The "for the want of nail..." proverb, which is somewhat related to FX_'s answer, the Butterfly Effect, in that both proverbs emphasize the power of insignificant things to cause momentous changes further on. However, in my observation, the Butterfly Effect is mostly referenced neutrally, and a few times even positively, say for example when describing the power of small act of kindness to enable the performer to reap larger "karmic" rewards later. On the other hand, the "for the want of the nail..." story usually has uniformly negative connotations, in emphasizing the role of unpreparedness in causing momentous tragedies in ventures of a complex nature.