Mariappa, 24, told BBC Three Counties Radio: "We will be keen to learn from last year.
"We faltered just after Christmas time and then we got dragged into a relegation battle."
He added: "We've got two victories in our last two games, and it's important over this Christmas period to pick up as many points as you can because the games come thick and fast."
December this year has already been an improvement on 2009, with victories over Leicester and QPR bringing a small dip in form to an end.
If we can get something out of the Scunthorpe game plus one win & one draw from the other matches we would have had a cracking Christmas
Chris00013
And Mariappa, who has been ever-present for Watford in the league this season, is desperate to come out of the winter programme as play-off contenders rather than relegation strugglers.
"This year we'll look to learn from that and look to pick up as many points as we can," he said.
"This league's all about consistency, those teams that stay the most consistent are the ones that end up promoted.
"That's something we're looking to do, just to be as consistent as we can, and not try and dip too much or be in and out of form, that's a big thing in this league."
Source: BBC Sport
Source: BBC Sport