United were beaten 3-2 after extra-time by Luton Town at Wembley on Sunday April 5.
That defeat was hard to take for the Iron players, who had been tipped as favourites to win the competition.
And, although that loss prompted a slump in the league which almost saw the side miss out on the play-offs completely, that was when Adkins knew his side had the character to come back to the national stadium and win.
"We got in a circle after that game and got rid of that horrible feeling, and we played some good football after that defeat and showed character yet again to stay in the race," he said.
"Fortune has favoured us in what was our 60th game of the season. We've assembled a group of players who will now have a chance to play in the Championship. It's a fantastic achievement to bounce straight back."
Adkins also had words of praise for the matchwinner Martyn Woolford, who has enjoyed an impressive first season in the Football League after signing from York City in the summer."We saw the potential in him and he's a flair player He's bided his time, got into the team and did ever so well," added Adkins.
"Kevan Hurst started the season on the left and we brought Martin to nurture him. He's bided his time, kept going, kept learning, worked hard and done very well for us."
Seven weeks ago Adkins' team were in tears on the Wembley turf after losing the Johnstone's Paint Trophy final to Luton by the same scoreline.
Kenny Jackett, the Millwall manager, set his sights on following in Adkins' footsteps by using this Wembley defeat as motivation for a promotion push.
"It's a hard one to take, there's no middle ground here - it's either elation or desperation," he said.
"We'll use that feeling to make sure we are doubly determined next season."