One is that life is a gift: before we got it, we weren't around to earn it. It's gratuitous, pure gift—like the existence of the world itself, really. So there's something wrong with us when we don't feel grateful for it, and we need to do whatever we must to be genuinely grateful for it. In our first president's wisdom, this is a day set aside for that.
People often overlook the obvious truth here and hence resist the corresponding duty. After all, there are many things about life, and even some lives themselves, for which there seems no cause to be grateful. That's a struggle of mine. I have a few long-running arguments with God that make it virtually impossible for gratitude to be my default attitude. I have a lot of company, which is why a bumper sticker that said "Let gratitude be your attitude" would offend as much as it would edify. It is a staple of my prayer life to remind myself that I ought to be grateful to God for creating and redeeming me. Somehow, of course, that doesn't seem enough. Thanking somebody purely out of a sense of duty seems like trying to make it by faking it. But then again, perhaps that's the best some of us can do for the time being—so long as we don't imagine we've arrived where we need to be.
The other obvious truth meriting restatement today is that Thanksgiving was instituted as a national holiday in order to thank God. For reasons well understood by any American involved with the institutions of the state, it is not politic anymore to make a point of that. That's why some people who should know better have forgotten it, and why thanking God now seems to be a private option rather than a public duty. In response, I can do no better than quote George Washington's words when he instituted the holiday:
WHEREAS it is the duty of all nations to acknowledge the providence of Almighty God, to obey His will, to be grateful for His benefits, and humbly to implore His protection and favour; and Whereas both Houses of Congress have, by their joint committee, requested me "to recommend to the people of the United States a DAY OF PUBLICK THANSGIVING and PRAYER, to be observed by acknowledging with grateful hearts the many and signal favors of Almighty God, especially by affording them an opportunity peaceably to establish a form of government for their safety and happiness:"
NOW THEREFORE, I do recommend and assign THURSDAY, the TWENTY-SIXTH DAY of NOVEMBER next, to be devoted by the people of these States to the service of that great and glorious Being who is the beneficent author of all the good that was, that is, or that will be; that we may then all unite in rendering unto Him our sincere and humble thanks for His kind care and protection of the people of this country previous to their becoming a nation; for the signal and manifold mercies and the favorable interpositions of His providence in the course and conclusion of the late war; for the great degree of tranquility, union, and plenty which we have since enjoyed;-- for the peaceable and rational manner in which we have been enable to establish Constitutions of government for our sasety and happiness, and particularly the national one now lately instituted;-- for the civil and religious liberty with which we are blessed, and the means we have of acquiring and diffusing useful knowledge;-- and, in general, for all the great and various favours which He has been pleased to confer upon us.
And also, that we may then unite in most humbly offering our prayers and supplications to the great Lord and Ruler of Nations and beseech Him to pardon our national and other transgressions;-- to enable us all, whether in publick or private stations, to perform our several and relative duties properly and punctually; to render our National Government a blessing to all the people by constantly being a Government of wise, just, and constitutional laws, discreetly and faithfully executed and obeyed; to protect and guide all sovereigns and nations (especially such as have shewn kindness unto us); and to bless them with good governments, peace, and concord; to promote the knowledge and practice of true religion and virtue, and the increase of science among them and us; and, generally to grant unto all mankind such a degree of temporal prosperity as he alone knows to be best.
Amen. Let us not forget.