President Barack Obama has called the now-ending session of Congress "the most productive" in generations.
He was speaking after the Senate approved a nuclear treaty with Russia, a bill to allow gays to serve openly in the military and other measures.
He said his "biggest disappointment" was the Senate's failure to approve a law to grant legal status to some young illegal immigrants.
Mr Obama was later to fly to Hawaii for his year-end holiday.
The president's year-end news conference came at the end of a so-called lame duck, post-election session of Congress in which Mr Obama and the Democrats racked up a series of victories that stunned observers accustomed to partisan bickering and gridlock.
In addition to approving the New Start nuclear arms treaty with Russia on Wednesday, Congress in the past week has approved a bill to repeal the "don't ask, don't tell" ban on gays serving openly in the military, a measure to fund healthcare for rescue and clean-up workers at New York's Ground Zero, a compromise tax cut and unemployment benefits bill, and other laws.
Earlier this year, Congress approved Mr Obama's healthcare overhaul bill, a financial services reform bill, and other Democratic priorities.
"It's fair to say that this has been the most productive post-election period we've had in decades," Mr Obama told reporters. "It comes on the heels of the most productive two years that we've had in generations."
'Victory for the people'
Mr Obama declined a reporter's invitation to gloat.
"What's happened over the last several weeks is not a victory for me, it's a victory for the American people," he said. "The lesson I hope that everybody takes from this is that it's possible for Democrats and Republicans to have principled disagreements, to have some lengthy arguments but to ultimately find common ground to move the country forward."
On the heels of Mr Obama's successful push to overturn the ban on gay and lesbian Americans serving openly in the military, the president declined to say he supported gay marriage.
But he suggested he was open to legislation that would give gay "civil unions" the same legal protections and status as mixed-sex marriages.
"I struggle with this. I have friends, people who work for me who are in powerful, long standing gay or lesbian unions," he said. "My baseline is a strong civil union that provides them the protections and the legal rights that married couples have."
One top Democratic priority that failed at the weekend - which Mr Obama called his "biggest disappointment" - was a bill that would have granted some young illegal immigrants who arrived in the US as children a path to legal status after they served in the military or attended university.
The bill failed under virtually unanimous Republican opposition, but Mr Obama pledged to work at it again in the next session.
The next session of Congress, due to begin on 5 January, will be far less friendly to Mr Obama and the Democrats' legislative agenda. In the November election, Republicans won control of the House of Representatives and strengthened their numbers in the Senate.
But Mr Obama on Wednesday said he remained optimistic.
"We are not doomed to endless gridlock," he said. "We have shown in the wake of the November elections that we have the capacity not only to make progress but to make progress together."