It could also guide coach Warren Gatland’s team selection for the global showpiece tournament in Japan starting in September.
"For every game at international level, you know that you can’t slip up," Moriarty told the Welsh Rugby Union website (www.wru.wales) on Wednesday.
"I say to myself every time that we go into a game that I am fighting for my spot. One mistake could mean I am out, and nobody wants that."
Ireland are the defending Six Nations champions and could yet retain their crown if they win and Scotland grab a surprise victory over England at Twickenham this weekend.
Yet with Wales on a 13-game unbeaten run and growing in momentum over the past 12 months, Moriarty says they are determined not to fail at the final hurdle.
"This is my first opportunity of doing this (winning the Six Nations) and it’s what we set out to do at the beginning," he said.
"Apart from winning a World Cup it is the biggest thing for anyone in the northern hemisphere, so I’d be really happy to achieve one.
"We’ve been building nicely over 13 games and against Ireland we won’t take a backward step to try and continue the streak."
Only Scotland (eight) have scored fewer than Wales’ nine tries in the Six Nations this year, with their success built less on expansive attacking play and more on organisation.
Their rock-solid defence has conceded only six tries in four matches.
"Sometimes people don’t see the hard graft but against Scotland (last weekend) it showed across the board with all the forwards and all the backs, it was a big, heavyweight slog.
"We’ve had some difficult games in the Six Nations but we are ready to go again. There’s been a lot of hard graft, a lot of carries, a lot of tackles, but it’s been nice to get the games in and build up some momentum."
(Reporting by Nick Said; Editing by Toby Davis)
