Macron, a 39-year-old centrist elected in May, presided over the first cabinet meeting since the summer holidays on Monday ahead of a crucial few weeks for his pro-business programme.
A new poll at the weekend showed that only 40 percent of voters were happy with his performance in his first three months, broadly in line with other surveys which have also shown a sharp decline in his popularity.
"Some people predict the worst. We should never give in to the prophets of doom," he told his ministers as the start of the meeting, in comments broadcast on television. "But we are where we are to act, with determination," he added.
- France's Macron sees popularity fall to 40 percent: poll
- French parliament approves Macron's drive to loosen labour laws
On Thursday, the government is set to unveil the law it plans to pass to reform the French labour code, making it easier for companies to negotiate terms and conditions with their employees and weakening trade union powers.
The law, which will be implemented by presidential decree rather than being debated and passed in parliament, is contested by hard-left trade union the CGT and Macron's leftist political opponents.
"The country needs to be transformed and the French people know that," Prime Minister Edouard Philippe told a press conference, adding that labour reform was a key part of Macron's pre-election manifesto.
Despite the fall in Macron's ratings -- as well as his own -- Philippe pointed to reasons for confidence, including a pick-up in economic growth and the solid parliamentary majority won by Macron's Republic on the Move party in June.
Macron has promised a change in strategy for the months ahead which will see him give more interviews to explain why he sees his reforms as necessary, having been accused of being too aloof at the start of his term.
He said last week during a trip to Romania that French people "hated reforms", but that he was proposing a "transformation" that would fire up the country's economy and make it a leader in Europe.