Ian Baraclough says preparation was key as Northern Ireland kept their Euro 2020 dream alive by beating Bosnia-Herzegovina on penalties.
The game finished 1-1 after extra time in Sarajevo, but the two sides were finally separated in the shootout.
Liam Boyce struck the winning penalty to make it 4-3 after Bailey Peacock-Farrell had saved from Haris Hajradinovic and Edin Visca hit the crossbar.
Conor Washington also scored from the spot, having come into the match alongside Boyce as substitutes in the 119th minute with an eye towards a shootout.
It was the first time Northern Ireland have ever gone to penalties, but Baraclough said the team were “preparing for every eventuality”.
He said: "We talked about going into extra time, we worked on penalties last month and in the last few days as well.
Match report: Northern Ireland beat Bosnia-Herzegovina on penalties
"We knew it was going to be a tight game, we knew it would be the team making the fewest mistakes and that could take their chances.
“It was a really nervous, tight game.”
Northern Ireland started on the back foot and fell behind after 13 minutes when Rade Krunic scored the opening goal for Bosnia.
However the second half saw an improved performance, with Niall McGinn getting the equaliser and setting up a dramatic finale.
Baraclough went on: “When it goes to penalties, I don’t think anyone could fault either of the teams, put so much hard work into it.
“You win the game on penalties - you have to be respectful, and we understand that we’ve been pushed hard.
“For my team, I can’t describe how I feel about them really, I’m very proud of what they have achieved so far and the work they have gone and done.”
The game also marked a record-breaking 120th Northern Ireland cap for Steven Davis.
“We’re absolutely delighted,” Davis said. “We’re delighted to go through and we’ll look forward to the play-off final.”
Northern Ireland will now face Slovakia, who beat the Republic of Ireland on penalties, with hopes of reaching a second successive European championship.