Nick Clegg told Liberal Democrats to "stop looking back" and start "shouting our achievements from the rooftops" in a speech to rally party activists.
The Deputy Prime Minister said it was time to "move on" from damaging rows over the NHS and tuition fees as he insisted "we are in Government and it is a better Government for it".
Mr Clegg also lavished praise on Baroness Williams, an early critic of the Health and Social Care Bill who has since co-signed a joint letter with the party leader on the reforms, telling his party's spring conference rally it was down to senior party figures like her that that joined up. He added: "I would like to pay tribute to the outstanding work Shirley Williams is doing in the House of Lords to protect the NHS."
Last year's event was dominated by dissent over the coalition's controversial health shake-up.
The legislation was "paused" as a result of the outcry and opposition from NHS workers, and has since been amended more than 1,000 times.
But it is not yet clear whether the Government has done enough to placate the Lib Dem grass roots.
The conference is expected to vote tomorrow to consider a topical motion on the NHS on Sunday, which could prove embarrassing for Mr Clegg.
Speaking at a rally in Gateshead, the party leader said he has never "ducked fights".
"We've made some difficult decisions, not all of them popular," he is to say.
"But we made all of them with only one test in mind: What was the right thing to do for the country?
"And now it is time to move on. To stop justifying being in Government and start advertising being in Government.
"To stop lamenting what might have been and start celebrating what is. To stop defending our decisions and start shouting our achievements from the rooftops.
"We're in Government, and it is a better Government for it. Fairer, freer and greener.
"Lower taxes for working people. Fairer chances for our children. And the beginnings of a new, green economy that benefits everyone in every city, not just a few in the City of London.
"So: no more looking back. You can't drive if you're only looking in the rear-view mirror.
"We have to look forwards, to the better future that we are building for our children.
"So let's tear off that rear view mirror and look straight ahead. Let's get on with the job that we all came into politics to do. Making this a more liberal nation."
Mr Clegg was also supported by party president Tim Farron - who previously expressed concerns about the health reforms.
"We got three quarters of our manifesto into Government policy, so I hereby allow you to stop saying sorry for the quarter we didn't get," he will say.
"And if people wanted that missing quarter, well they should have flipping voted for us, shouldn't they?"
Mr Farron joked that he had turned down an invitation to attend the Brit music awards because if he wanted to spend a night with "half-cut prima donnas" he could go to Strangers bar - a reference to Falkirk MP Eric Joyce who today admitted four counts of assault following a night in the Commons pub.
He also branded Labour leader Ed Miliband "easily led Ed", claiming he had had 15 years to stand up to media mogul Rupert Murdoch.
Mr Farron said he "completely understood why membership may have slipped" but insisted the "fight-back starts here".
He launched a recruitment challenge urging each member to recruit three new or lapsed members in the next seven days.
He added: "Being in coalition is absolutely right so let's get over it."