When Congress convened in January, those who were watching got treated to a small but revealing moment: As John Boehner, the new minority leader of the House, was handing the House gavel over to incoming Speaker Nancy Pelosi, he looked out at the assembled members and told them, “Be nice.”

It might have sounded like a jocular and insignificant point, but if Congress follows any single admonition this year, I hope it’s that one.

In truth, it shouldn’t even need saying. For an individual legislator, cultivating congenial relationships with other legislators ought to be a matter of habit. In order to get anything done, especially if it involves legislation, you have to work constantly to line up support, convince others that what you want to accomplish matters, and make it clear that you’re worth listening to. Even if others don’t agree with your goals, they’ll still respect your efforts and at least listen to your arguments.

But being nice — and especially, treating others fairly — is at the moment as much a group imperative as it is wise personal custom. Congress has just emerged from an extended period in which fairness and decent treatment of others were too often banished, and it created a toxic environment on Capitol Hill.

The new Democratic majority has an opportunity to freshen the atmosphere, and every American has a stake in whether or not they make good on that chance.

For if there’s any single lesson to be gleaned from the Republican takeover after the 1994 elections or the Democrats’ this year, it is that the manner in which a majority wields power has enormous consequences.

If members of the minority party lose on issues of policy but believe that the process was a fair one, they might be frustrated, but they’ll abide by the results.

If, on the other hand, they feel constantly slighted, ignored, shut out of the legislative process and treated overall as if they have nothing to contribute to the national dialogue, they will seethe with resentment. They will do everything in their power to frustrate the majority. And, the vicissitudes of politics being what they are, they will eventually be put back in a position of power.

Which is why I was somewhat disconcerted to see that the new Democratic majority in the House, which certainly understands the sting of unfair treatment, has on occasion yielded to the temptation of its newfound power to shut down Republican participation. It did so during the vaunted “first one hundred hours,” barring Republican amendments to the package of bills it had prepared in order to make good on Democrats’ campaign promises.

This was neither a good precedent nor, as it happens, all that necessary: Having passed its bills in a hurry, the House now has to sit around and wait for the Senate to act. It also cost it the benefits of legislative vetting that a robust debate offers — as Democrats discovered when it became clear that the wording of a proposed ethics law forbidding members from flying in private planes meant that those who were pilots could not fly their own aircraft.

Then House Democrats did it again, preparing a budget to keep the government running for the rest of the fiscal year that allowed no GOP amendments. Again, there were arguments to be made defending their actions: Time was short, and leading Democrats pointed out that the entire exercise would have been unnecessary had the GOP-dominated Congress acted on such a measure last year.

But let’s be honest: The majority can always come up with reasons for taking shortcuts that allow it to act. That’s not the point. The point is that in our democracy, the process is every bit as important as the legislation it produces. Fairness and trust should be the coin of the realm.

Congress represents everyone, not just those who voted for members who happen to form the majority. Allowing the regular order of hearings, amendments and debate to flourish — with fair restrictions to keep it wieldy, if necessary — would go a very long way to healing the scars of the last few years and make it less likely that Capitol Hill will return soon to the ugly bitterness that cost it so much public good will and led to legislative stalemate.

Lee Hamilton is director of the Center on Congress at Indiana University. He was a member of the U.S. House of Representatives for 34 years.