There is a certain measure of ambition that must be present for a person to be successful, however, it must be balanced against compassion and reason. We must be ambitious enough to never be satisfied with what we have accomplished but compassionate enough to know when feeding our ambition will do harm to others; ambitious enough to work hard for what we want and reasonable enough to realize when the effort is not worth the gain.
Our ambition is our drive to do better. This may be measured in terms of wealth, standing, philanthropy, knowledge or fame. Ambition is more than just wanting these things, it is a willingness to work for them. It is the machine that turns dreams in to reality.
Ambition can also be destructive. When it becomes too intense, when the desire to have out weighs reason and compassion it can hurt people. The goal of ambition should not be greed but the betterment of one's situation.