The Central American nation have been the surprise packets in Brazil, coming through a difficult group on their way to the quarter-finals.
A last-eight clash against the Netherlands on Saturday is Costa Rica's first ever quarter-final outing at a World Cup, having only surpassed the group stages once before (1990).
"We know we're doing something so big for the people back home, but maybe we don't realise the extent of how big just yet," Ruiz told FIFA.com.
Ruiz added: "Maybe in a few months this will all sink in, but for right now we're just trying to enjoy what we're living."
The Dutch, World Cup runners-up in 2010, are heavy favourites for the clash at the Arena Fonte Nova in Salvador.
Ruiz said his team were still desperate to go further despite their remarkable achievements thus far.
"We have nothing to lose," he said.
"We've come so far and done so much, but we want more. We want to continue on and see how far this can go."
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