CHRISTMAS IS always the most private of the holidays. The city nearly comes to a stop. People repair to homes, friends and families. But there is usually news from abroad to remind you, amidst all this local good cheer, that things are not going so well elsewhere. This year, the events in Poland weigh on the season here. President Reagan caught the juxtaposition between the American Christmas and the Polish Christmas in his address Wednesday evening, and he offered a useful example of the manner in which Americans ought to respond.

The president's tone was cautious, measured and right. The United States will now begin to apply a series of economic sanctions--but only rather minor sanctions with a limited effect for the present on Polish life. They are not designed to add significantly to the disruption of an economy already severely damaged. They are meant as a precedent and a warning. If necessary, this country is prepared to go further, Mr. Reagan said. The United States' next steps will depend on Gen. Wojciech Jaruzelski's next steps.

Mr. Reagan is well aware that American policy is going to have to be finely calibrated. It is not morally permissible to take any action that might incite unarmed Poles to greater conflict with troops--Polish or, even worse, Russian. American initiatives in Eastern Europe always have to be accompanied by recollections of 1956, when this country encouraged a revolt in Hungary and then was unable either to help the rebels or to restrain the Soviet repression that followed. In the present case, the United States wishes to penalize the Polish government that Gen. Jaruzelski heads, but it does not wish to increase the distress of the Polish people. The present formulation is not entirely satisfactory. Mr. Reagan knows as well as anyone that food deliveries, even if directly to the people, take some of the pressure off the Polish government. But presumably this country will at least find ways of letting the Poles know where the food is coming from.

More important, Mr. Reagan has offered this country's assistance to Poland in rebuilding its economy, if Gen. Jaruzelski lifts martial law and restores a measure of freedom to the Polish people. That is an offer in which Mr. Reagan is unquestionably supported by the great majority of Americans. It holds out a possibility --and perhaps the only possibility--of reversing the dire decline in Polish standards of living that otherwise appears to be inevitable.

That leaves the initiative with Gen. Jaruzelski. The truly crucial question is whether he and those he represents are willing to allow Solidarity to exist under any terms, and to allow Poles any real degree of freedom at all. The prospect is not very hopeful, but it is a prospect worth pursuing. Only time can tell what the general intends to do. Mr. Reagan has let the general, and the Russians standing behind him, know that they can expect an American reaction. But, wisely, he is giving them a little more time to consider.