Prudence: It allows us to judge correctly what is right and what is wrong in any given situation. Doing the work of God shows good prudence. Doing the work of the devil shows poor prudence. Because it is so easy to fall into error, it is essential that we seek the help of others. Disregarding the advice of others is considered imprudence. Regarding the advice of others is prudence. Prudence helps us decide what needs to be done.
Justice: It is giving everything and everyone it's rightful attention. We must not judge based on personal views, we must judge based on what is true. For instance, if we owe someone money, we must pay him the money we owe, regardless of whether we like that person. If we are deciding on whether something is legal or not legal, we must make our decision based on the law of the land, not on our own personal political affiliation. It is doing what is right regardless of our opinion. Justice helps us decide what needs to be done.
Fortitude: It is the ability to conquer fear and remain steady when facing obstacles. It's the restraint of fear so we can act. Fortitude gives us the strength to do what needs to be done. Fortitude is also the only cardinal virtue that is also a one of the seven gifts of the holy spirit.
Temperance: It's the restraint of our desires and actions. While food, drink and sex are all needs, too much of of any of them can have undesirable consequences. Temperance prevents us from overindulging.