Writing in a New Year message to party members, he warned of continuing economic uncertainty but said ministers would "stay the course on the deficit".
He said Lib Dems were "about" a fairer society "where everyone can get on".
And he said the Olympic year featured "shared experiences" and he anticipated "more great moments" in 2013.
"The last 12 months have been lit up by moments that will stay with us forever," he said.
"When Mo Farah approached the final stretch of the 10,000m final, who wasn't up on their feet, screaming at the TV?"
The year ahead, though, would feature "big challenges", he said.
"Many families are still feeling the squeeze.
"Look at the world around us and you see continuing economic uncertainty - particularly in our European backyard. We are living through fluid, difficult times.
Continue reading the main storyI want you to hear it from me, on behalf of the Liberal Democrats, that this coalition government is not going to lurch one way or the next”End Quote Nick Clegg "What I can tell you is that, whatever 2013 throws at us, the Liberal Democrats will continue to anchor this coalition in the centre ground and we will hold firm to our key purpose in this government."
The Liberal Democrats were "building a stronger economy, in a fairer society, enabling every person to get on in life", he added.
He said people deserved "the reassurance that your government has a plan to steer the country onto better times - and that we're going to stick to it".
"So I want you to hear it from me, on behalf of the Liberal Democrats, that this coalition government is not going to lurch one way or the next."
In the New Year, the coalition will publish a mid-term report setting out plans for child care, transport, social care and youth unemployment.
"We will stay the course on the deficit," Mr Clegg said.
"We will cut income tax bills and help with childcare bills. We will invest in boosting jobs and we'll reform welfare to get people into work."
BBC political correspondent James Landale said that both the coalition and Mr Clegg had experienced their share of problems in 2012.
Mr Clegg had lost a Cabinet minister to an alleged traffic offence, lost his plan to reform the House of Lords and "lost loads of elections".
The economy had double-dipped and forecasts were grim, our correspondent added.
But the small flicker of optimism was that the Lib Dems and the Conservatives had remained united on cutting the deficit.
