Uefa Champions League winners Real booked their place in the final in Marrakech with a 4-0 victory over Cruz Azul, while South American champions San Lorenzo required extra time to see off Auckland City 2-1.
Casillas has reclaimed his place in the Real first team this term, having fallen out of favour in recent seasons, and the 33-year-old believes he is beginning to rediscover his best form.
"I don't think I have anything to prove – what I've done in my career is there for everyone to see," he told FIFA.com. "By playing games I'll hopefully get my confidence back to where it used to be, which is what excites me more than anything.
"I feel on a high."
Casillas saved a Gerardo Torrado penalty with Real 2-0 up in their semi-final - a moment coach Carlo Ancelotti described as key in his side's progression - and the Spain international agrees that there could have been a different outcome had he conceded.
"If it had gone to 2-1, it might have been a whole different ball game," he continued. "Goalies always try to help their team at crunch moments like that.
"Luckily I dived the right way and I'm happy because the team were able to relax and see it out comfortably."
The result has given Casillas a second chance to lay his hands on one of the only pieces of silverware yet to grace his bulging trophy cabinet, having finished fourth with Real as a 19-year-old in 2000.
"I played in this tournament 14 years ago, but I wasn't able to win it," he added. "I hope to win the title now because it would mean another photo for the history books, both for Madrid and for me personally.
"There's nothing more satisfying for a player than bringing more joy to this club."
Real Madrid are enjoying a winning run of 21 matches in all competitions - three short of the world record held by Curitiba - but Casillas knows the sequence must end somewhere.
"Winning 21 games in a row is very difficult, but we have to keep our feet on the ground and be mindful that this run won't last forever," he said. "One day a defeat or draw will come, but we're not thinking beyond Saturday's match and getting win number 22.
"What's important is for us to win on Saturday because if we don't, I can guarantee you that all the headlines in the papers will look different."
Sergio Ramos, who this week denied claims he was looking to leave Real, is set to feature, despite leaving the field injured during the semi-finals.
Though the odds are stacked against San Lorenzo following their stuttering semi-final, striker Mauro Matos - who netted the winner - has not ruled out a shock triumph.
"They're one of the top two teams in the world, if not the best, but it's 11 against 11 on the pitch," he said. "We know what we have to offer and we're going to believe in ourselves.
"Anything could happen."