Ronny Rodelin scored the only goal of the game inside the first minute of the second half shortly before Franck Beria was shown a red card during the 1-0 victory at Stade du Hainaut, which keeps Lille at pace with league leaders Paris Saint-Germain.
"It wasn't easy," Girard told reporters. "We went through the full set of emotions. We controlled the game for a spell, and then we scored at a good time, at the start of the second half. Then the sending-off of Franck [Beria] penalised us a little but I think the team showed that they have real heart and that we can count on them.
"We fought well and I think, even when down to 10 men, we caused Valenciennes problems. It would have been better had we finished the game with 11 men because we used up a lot of energy [after the red card], but it is a great win and the kind of result that brings everyone together.
"As long we keep the same spirit, things will go well for us. Now we need to recuperate. We have some boys who are fresh, others less so, but we just have to get on with it."
Lille are currently second in Ligue 1, four points adrift of leaders PSG.