Relegation-haunted Reading travel to Crawley for Saturday's third-round tie having pieced together an encouraging Christmas that yielded four points from three matches.
Critical fixtures against West Brom, Newcastle, Chelsea and Sunderland await over the next four weeks and Mariappa insists dispatching Crawley - whose director of football is former Royals boss Steve Coppell - will provide a welcome shot in the arm.
"You want to go as far as you can in every competition and it's good to get runs in cups - it breeds a lot of confidence if you can go through," he said.
"It'll be a tough game though and we'll all prepare right mentally for it. We know what to expect from the FA Cup.
"I've been lucky enough to beat teams when I've been the underdog or when we've been the favourites. It doesn't matter - anyone can beat anyone, that's the magic of the FA Cup.
"We're all used to games coming thick and fast. We want to get through to the next round but we'll also use it as preparation for our next league game."
Mariappa insists Reading were left smarting after failing to claim any reward from Tuesday's trip to White Hart Lane, where Tottenham won 3-1, and insists their Premier League obituary has been written too soon.
"We had a couple of good chances and had we taken them maybe we could have sneaked a draw, but it's a tough place to go," he recalled.
"The lads were putting everything into it for each other, putting themselves in front of everything they threw at us. With the game at 2-1, we could have so easily nicked a draw.
"There's a great spirit here and we're definitely not giving up. The media have written us off, but we were written off before the season started.
"We're confident we can put together a good few results and we're looking forward to the next game."