Philippe Saint-Andre saw his first game in charge of floundering Montpellier end in a 24-20 defeat by Lyon on Wednesday but the former France coach vowed to keep the team in the elite Top 14 even if it meant surviving on "three, four hours sleep".
Saint-Andre, who had been the club's director of rugby, was named head coach as well after Xavier Garbajosa was sacked last week.
However, Wednesday's defeat -- their eighth in 11 games this season -- left Montpellier second from bottom of the table.
"I had forgotten what it was like to sleep three or four hours, to think only about the management of the team," said Saint-Andre who was French national coach from 2011-2015.
"I am here for 16 games, to keep Montpellier in the Top 14. We won't give up until the last day.
"It's an exhausting job, a job for young people. But I will do my 15 hours a day and stop at the end of June. That's the deal I made with my family."
Montpellier trailed 21-7 to play-off hopefuls Lyon at half-time at Stade Gerland before dominating the second period to secure a losing bonus point.
Skipper and fly-half Jean-Marc Doussain, scrum-half Jonathan Pelissie and back-rower Patrick Sobela scored Lyon's three tries, all in the first period.
Georgian prop Levan Chilachava, in the 33rd minute, and a 44th-minute score for replacement fly-half Vincent Martin gave Montpellier their two tries.