Arsenal manager Arsene Wenger accepted his side were "a bit lucky" after a fumble from Reading goalkeeper Adam Federici handed them a 2-1 extra-time victory and a place in the FA Cup final.
The Gunners will head back to Wembley on May 30 aiming to defend the trophy after edging past the Sky Bet Championship side, who had rallied after going behind just before half-time to a fine goal from Alexis Sanchez.
Reading drew level on 54 minutes when Garath McCleary's volley was deflected past goalkeeper Wojciech Szczesny, who could only palm the ball back over the line.
In the end, an error from Australian Federici proved so costly, the keeper allowing a low, angled shot from Sanchez to slip through his legs and roll over the line on 115 minutes.
"It was a difficult game against a well organised, resilient, committed and physically strong Reading team," Wenger said.
"They really wanted it Reading, they were willing to die on the pitch to go to the final and you have to congratulate them for the effort they put in.
"In the end, we were a bit lucky because their keeper made a mistake and I can understand that he is distraught, but as well he kept them in the game for long periods."
Wenger added: "What was missing was a bit of speed of combination and sharpness in the final third maybe, but overall the concentration was there.
"I don't think we switched off (for the goal), but after half-time we did not come on with the same intensity. We started to suffer and we paid for that."
Arsenal have reached a record 19th FA Cup final, and will be looking to overtake Manchester United's mark of 11 victories, with five coming under Wenger's tenure.
"Now, let's focus on our next game, we come back here in the final, but we have time to prepare," Wenger added.
"The final is a 50-50 (game). If we can beat the record we will be very happy. Let's hope we have all of our players available and come back in good shape."