On Saturday, Poland and nine other countries will join the European Union.
"This event will decide the role and significance of our nation in Europe during long years in the future," the Polish bishops stated in a recent note reported by the Italian bishops' SIR news service.
The prelates invite Poles to regard this step "with confidence," without fearing "the loss of our national identity and sovereignty."
Cardinal Jozef Glemp, primate of Poland, has invited the faithful to fast on bread and water on this Friday morning as a spiritual preparation for the EU entry.
The bishops' document mentions issues of concern for the country's future.
The antidote to a weakening of the "rich national religious traditions" lies in "profound reflection on the spiritual dimension of our identity, as the pre-condition for a fruitful dialogue in truth and freedom" with other members of the enlarged European Union, the Polish bishops' conference states.
Aware of the spread of secularization throughout the continent, the bishops call Poles to consistency between their religious values and their application in the various realms of daily life: family, work, culture, science, the economy and politics.
Christians have a role at all levels, including the political and economic, in the new European Union, the bishops said.
They noted that "the year of change of 1989, inspired by the desire for freedom, found its vital sap and the strength to grow in the countries of Central and Eastern Europe, stemming from a primary religious motivation."
In a second document, the Polish cardinals and bishops highlight the "Responsibility of Christians to the Homeland."
After appealing for the unity of believers in Christ, at this key moment of national life, they appeal to citizens "not to support those politicians and forces that promote values that undermine life and the family."