We might take a very practical view of this philosophical question, though even a practical view potentially has profound implications.
The notion of human interconnection is undeniable, though the power of how much one person's decisions might influence another person's life is debatable. However, if we assume that due to the fact that none of us actually live in true isolation, we can see quickly that decisions made by one person will affect others.
At work, if one person is a little bit sick and decides not to come in to work, the work load of the day may be shifted to others. This can potentially have a domino effect, causing a co-worker who is also a little bit sick but who came in to work to struggle through the day. The stress of this struggle might manifest itself in any number of ways later.
Seen in a slightly different light, we might take figures like Gandhi, Martin Luther King Jr. and other moral leaders as examples of people whose choices have a definite impact on other people and on the culture around them. By choosing non-violent resistance, these particular leaders had a lasting effect on their societies and an immediate effect on the culture of the struggles in which they were involved.
This is a profound question. I think that to a great extent that the answer to the question helps to determine an individual's core belief about the nature of individual consciousness. If one believes that individual actions do not impact or are made in a vacuum apart from impacting others, there might be a correlative belief that human beings are all alone in the world without the presence of a divine force. In contrast, if one believes that individual action does impact others around them, there might be a similar belief that human beings are not alone and that there is a divine force that helps to guide individual action. Such a question might be able to reveal more than answer to it, but the nature of who we are and what shall we do. Certainly, the discussion is not an automatic, iron clad guarantee of whether or not one believes in God, but rather helps to see how such answers reflect the larger belief in the divine.
The choices we make determines our actions. Our actions are then perceived by others, and impact them in various ways depending on the nature of our actions and their situation and psychological characteristics. People thus affected react to our actions just as they react to any other situations or events occurring in their environment.
In this way our decisions and actions first impact the thoughts and feelings of those around is. These thoughts and feelings in turn influence their actions. One important and practical implication of this reality is that the best way to influence the behavior and action of others is to change our own behavior, so that it will increase the probability of eliciting desired response from others.