Nick Clegg will tell party members to "stop lamenting" and start celebrating being in government, as the Lib Dem spring conference begins in Gateshead.
At a rally, he will say it is time to "move on" from justifying being in government and to start advertising it.
The deputy prime minister faces the prospect of a debate and vote on the controversial NHS bill on Sunday.
Labour's Andy Burnham has urged Lib Dem activists to help stop the bill, in an open letter on a Lib Dem website.
Last year, discontent expressed at the conference about the NHS shake-up was followed by a "pause" on the bill - something Mr Clegg puts down to Lib Dem intervention.
This year an "emergency motion" has been submitted calling for the changes to be scrapped.
The motion says the Lib Dems "oppose the further commercialisation of the NHS" by "working together to achieve the defeat of this deeply unpopular bill".
It is not guaranteed to be debated, but BBC News Channel chief political correspondent Norman Smith, in Gateshead, said there was mounting pressure to get the bill dropped - and people close to Mr Clegg had accepted there would be a vote.
If he lost the vote - it would put Mr Clegg at loggerheads with his party, just days before the final day of debate in the Lords on the bill.
It comes as the government is ordered to publish its transition risk register, which compiles possible dangers related to the shake-up of the NHS in England, under Freedom of Information laws.
Mr Clegg has urged his party to get behind the bill, saying it is now "undoubtedly better" because of the efforts of Lib Dems.
In a speech at a rally in Gateshead on Friday evening, Mr Clegg will tell party members he has never "ducked fights".
"We've made some difficult decisions, not all of them popular," he is set 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."
Mr Clegg will say the government is "fairer, freer and greener" because the Lib Dems are part of it.
And insisting there is "no more looking back," he will urge activists to look forward 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," he will add.
Mr Clegg will also be supported by party president Tim Farron - who has called for further NHS bill concessions.
The Health and Social Care Bill's proposals include giving GPs control of much of the NHS budget and opening up the health service to greater competition from the private and voluntary sector.
These have proved controversial, with critics - including some Lib Dems - warning of "back-door privatisation".
Lib Dem minister Andrew Stunell told the BBC's Daily Politics that "some very important figures in the party including Shirley Williams will be saying this is the right bill to pass" at the conference.
But shadow health secretary Mr Burnham wrote on the Lib Dem Voice website: "I know that many Lib Dem activists know in their heart of hearts that this bill is bad for the NHS. This weekend in Gateshead, please tell that truth to power."