To begin with, the question of defining peace is a philosophical one which is why it will probably be quite hard to find an easy answer right away. What is more, one should also take into consideration the fact that different people have different attitudes.
In other words, for some people peace may be achieved only when they do not have any problems. In this situation they will have nothing to worry about which means that they will obviously remain calm and peaceful.
However, it is quite difficult not to have any problems nowadays as there is always something we are worried about. In addition, there is always at least one problem we need to solve which is why peace should probably be viewed as the ability of the person to deal with those problems as well as to have a positive attitude no matter what. Sometimes the ability to accept the situation is much more important than racking your brains trying to find a solution that is going to work.