Relegation-haunted Reading travel to Crawley for the 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."