Gareth Ainsworth has admitted that he was worried throughout the 90 minutes against Fleetwood on Monday.
Joey Barton's Cod Army had most of the possession at Adams Park, but the Chairboys still managed to get on the scoresheet twice as the game ended 2-2.
The game was finally settled when Fred Onyedinma scored an injury-time equaliser on the night, which sent Wycombe to Wembley.
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The manager said: “I was worried throughout because we're up against a team that's a very good side.
“We knew that we hit them really well on Friday night (July 3) and we didn't let them settle, we looked fit, we looked sharp.
“It's almost like we couldn't have reached those levels again because we've been so intense on Friday.
“But it's the two-legged affair, you have to count both legs and both legs say that we've won the game 6-3.
“They played a great system.
"We had to change.
"They changed their system, which again, is respect to my boys, forced them to change their system, come with a very attacking line-up and a very attacking system.
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“I'm just really, really proud that we've dealt with what we have to do.
“Myself and Dobbo were racking our brains at times on the touchline, trying to counter things.
“That's just the word really for that second goal, we countered them and Fred Onyedinma with a brilliant finish.
“I'm just so proud that the boys celebrated the way he did, made it count the way they did and we're at Wembley, which is amazing.”
Wycombe face Oxford on Monday, July 13 at Wembley.
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