WHEN A. LINCOLN left Springfield, Ill., for Washington 120 years ago, one day before his birthday, more than a thousand well-wishers gathered at the railroad station early that morning for a proper send-off.

Mr. Lincoln was at his sentimental best in thanking friends and neighbors: "To this place, and the kindness of these people, I owe everything. Here I have lived a quarter of a century, and have passed from a young to an old man. Here my children have been born, and one is buried. I now leave, not knowing when, or whether ever, I may return." Accompanied only by a handful of companions, he then boarded his train and was off.

Another Republican president with a February birthday has just completed a somewhat more elaborate round of celebrations, one that followed hastily on the inaugural festivities. Mr. Lincoln left his friends behind in Illinois, but Mr. Reagan's circle appears to have managed the shift from California to Washington society intact and still restless. "After this weekend," one of them observed of the birthday events, "we may almost be partied out -- almost."

Although the friends of Ronald Reagan doubtless have some good toots left in them, the president himself may soon be "partied out," if only out of political common sense. Maintaining too high a social profile runs the risk of sending the country a stylistic message far different from the call to sacrifice that Mr. Reagan made in his televised talk on the economy.

The problem is a familiar one for new presidents. Normally, their emotional separation from home and section begins sometime before Inauguration Day and then proceeds fitfully until the incumbent comes to terms with his enforced residence in Washington. In this way, Mr. Reagan left California "not knowing when, or whether ever" he would return. As for California, that portion of its citizenry not remaining in town to help him govern finally seems on its way home from the ball. The party is definitely over, and the guest of honor here to stay.

Mr. Reagan has shared with the press his fondness for the remark Mr. Lincoln made to newsmen the day after his election: "Well, boys, your troubles are over now, mine have just begun." On that occasion, Mr. Lincoln was only partially correct.His troubles and the concerns of the press had blended and would remain interwoven during the agonizing war years ahead.

Throughout the Civil War, only two private secretaries guarded him against the tide of visitors seeking patronage, policy decisions, news items and every conceivable form of personal favor. Yet an exhausted Mr. Lincoln managed somehow to endure his presidential ordeal with humor and composure substantially intact. President Lincoln thrived on what he called the "public opinion baths" provided by press and other Washington visitors. He chose not to isolate himself even from the least friendly and most demanding of them: "I must run the machine as I find it." These cautionary words on Washington served President Lincoln and the nation well at the time, and a similar dose of melancholy realism may have a certain usefulness at this moment of imminent change and high expectation.

Happy Lincoln's Birthday, Mr. President.