Rahm has won six times on the European Tour and four times on the PGA Tour. His best result in a major was a fourth place finish at the 2018 Masters. He also tied for fourth that same year at the PGA Championship.
"I'm still trying to figure out how the rapid ascent in golf that I had, made it a little bit awkward in some major championships," he said. "Major championship golf is not just about playing good. It's more a mental test than anything else.
"I've been having some good showings and somewhat close calls, but I'm ready to have a better chance on a Sunday."
Because of the dangers of Covid-19, the 2020 PGA will take place with no fans, which is a first. Players, caddies and officials are all tested for the coronavirus before entering the grounds.
The PGA Championship is the first major of 2020 and the first in over a year. That's the longest wait between majors since the 1940s. Rahm said the time off has given him a new appreciation of the sport.
"The reason for us not playing in a couple of the majors, it's a sad reason," he said. "At one point it looked really ugly with how things were in California and New York.
"If you've seen the locker room this week, all the lockers are ten feet apart. It's unbelievable, right.
"I'm really thankful for everybody involved in it and thankful we can keep playing golf."
Rahm says he has been using meditation and writing a journal to occupy his time during the Covid-19 isolation.
"I'm a person who likes to write and journal. Stretching, meditate, whatever. Whatever it is, honestly, that's going to make me feel useful.
"I'm big in writing more than meditating. That's my sense of peace of mind, at least"
Rahm will tee off Thursday in a group with Phil Mickelson and fellow Spaniard Sergio Garcia.