The 40-year-old admits there were some encouraging signs from the loss to Brest as France saw its first female coach in men's professional football make her competitive debut
Clermont took the lead before suffering a 2-1 reverse to Brest, with Alexandre Alphonse netting the winner midway through the second half.
The game was broadcast live in France as Diacre took charge of her opening competitive match as the first female head coach in men's professional football in the country.
Diacre was disappointed at the way her side utilised the ball during the defeat but acknowledged there were some promising signs for the season ahead.
"It's never fun to lose, that's obvious," she told Eurosport after the match. "We've slipped up against a good Brest team that performed well. We made two errors for the goals we conceded. That's how it is.
"But we did good things, which bodes well for the future.
"Today, we haven't had hold of the ball. That was one of our weaknesses. We haven't used the ball, we haven't developed our play as we could have done, as we should have done. That's what put is in trouble.
"I will remember the defeat, but I'm still proud of my players because they gave so much. I'm proud of their performance tonight."
Diacre was appointed Clermont boss after Helena Costa resigned less than a month into the job following a dispute with the club's management.
The 40-year-old was presented with flowers prior to the match by opposite number Alex Dupont to mark her birthday.