Salah had to be substituted in the first half of the final four years ago after being hauled down by Sergio Ramos, with Real going on to win 3-1.
"I remember when I went out after 30 minutes or something, it was the worst moment of my career," Salah told reporters on Wednesday.
"I was really, really down after that. After the game I knew the result because I was in the hospital. I was like, 'We cannot lose the game in that way.' I never had that feeling before in football."
Liverpool defeated Tottenham Hotspur in the final of Europe's elite club competition a year later but the 29-year-old Egyptian said he still had unfinished business with the Spanish champions.
"After what happened with Madrid last time and also after what happened on Sunday. Everyone is motivated to win the Champions League," said Salah, who has scored eight times in this season's competition.
"This is an unbelievable trophy for us and every season we have fought for it since I have been here."
Liverpool, who have won the League Cup and FA Cup this season, had their bid for an unprecedented quadruple of trophies foiled by Manchester City last week after Pep Guardiola's side beat them to the Premier League title by a single point.
