He also spoke about his own goal against Brighton that cost them two points in their recent Premier League game.
Mariappa hopes to be at his best as the Hornets take on Manchester United at the weekend.
"Fozzy [Ben Foster] was there, not letting me dwell on it and just picking me up straight away and that's part and parcel of football," he told Sky Sports.
"You're putting your body on the line for your team and obviously it's disappointing when you make mistakes, especially when it costs the team.
"But it's about how you move on as a collective group and we're a strong group here and that's how we need to be for the rest of the season going forward."