Iago Aspas struck Celta's winner on 84 minutes.
Giraldez said: "I'm happy to start with a victory, we hadn't started winning for many years and we always choked on the first day. I'm also happy with the reaction and with the spirit of a team that wants to win.
"We are a team that wants to compete, even if we don't have a clear day we are capable of recovering and looking for other weapons. I think we didn't play well, we had a game that we could have perfectly lost.
"It has been a Russian roulette for several moments. The message is clear. In the first half we played tied, in the second at least we were brave and we ended up winning the game.
"In the first half, more of what they wanted happened, there was little play, low pace of the game, and in 2 or 3 lateral crosses they created danger for us, by not adjusting the cross situations well. We didn't finish being deep, circulating the fast ball."