United achieved the result without Wayne Rooney on the pitch.
Park said: "We needed three points. We know Valencia have been doing well this season. But we were sharp defensively and we prepared well.
"At the end of the game we managed to score. It was enough to win and get three points. The past has gone. We look forward to the future. Maybe today a win is another step towards improvement.
"Throughout United's history we always come up with answers to problems. Big stars come and go but still United keep producing the same performances. We just concentrate on that to make sure we show our quality on the pitch."