The champions bounced back from their 6-1 home thrashing by Manchester City with a hard-fought 1-0 win at Everton in the Barclays Premier League on Saturday.
Sir Alex Ferguson's side now face Otelul Galati in midweek hoping to take another step towards the Champions League knockout stages before hosting Sunderland at Old Trafford next weekend.
Park said: "It was very important for us - we had to get back to winning ways after the defeat against City.
"The boss told us that in the club's history, we always get over [bad results]. He encouraged us to play and be confident.
"We had to show that and the players had to fight to win the game and the determination was great.
"Goodison Park is always a hard game for us, we have had difficulty there. We had to win the game."
United's form has generally dipped over the past month but, with a relatively kind run of fixtures ahead, Park believes momentum can be built.
The Korean, 30, said: "It is very important to improve ourselves for the rest of the games. Hopefully we can continue to play like that."