Final answer:
Brutus implies that seizing critical opportunities when they arise can lead to success; failure to act may result in a life of hardship and regret.
Step-by-step explanation:
When Brutus tells Cassius, "There is a tide in the affairs of men / Which, taken at the flood, leads on to fortune; / Omitted, all the voyage of their life / Is bound in shallows and in miseries," he means that there are moments in life that present great opportunities, and must be taken when they arise. If these opportunities are missed, the rest of one's life may be filled with difficulties and dissatisfaction. This metaphor suggests that acting decisively at the right moment can lead to success and a better future, whereas hesitation can result in missed chances and regret.