El Tri claimed the first major scalp of the tournament on June 17 as Hirving Lozano's goal in Rostov proved enough to down the reigning world champions.
Up next for Mexico is a meeting with the Taeguk Warriors, who struggled in a 1-0 loss to Sweden on Monday.
"We have to keep playing as well as we did against Germany and we have to have the same mindset," Guardado told reporters on Friday.
"We don't get extra points when we beat Germany. We cannot relax and sit back. We mustn't think of our victory against Germany as something with more value.
"Everybody on the team is aware of what is at stake. The victory against Germany has even reinforced the mindset we've had for a long time now. It's made us feel stronger.
"Tomorrow I have absolute trust in my teammates because we will demonstrate what we did against Germany."
Mexico and South Korea have met once at the World Cup, the Central Americans winning 3-1 in the 1998 group stages.