Goals in each half from Liam Davis and Michael Uwezu handed Johnson his first win in an ill-tempered clash, with Luke Foster and John Mousinho dismissed for the visitors.
"Everyone connected with the club realised the importance of this game, including the players, and they went out there and played with a real passion to get us the result," said Johnson.
"We gave a professional performance and for the first time we saw the game all the way through and I'm very proud of the way we played.
"It was never going to be a fluent game of football but you need passion for these sorts of games and if you have that then you have a chance of winning them.
"It was important for us to get a second goal when we did and great to keep a clean sheet and that owes a lot to the players being prepared to put their bodies in the way and also goalkeeper Chris Dunn who was desperate to play all week despite having a facial injury. Now we know which level we're playing at next season we can start planning for that because we do need to turn things around here."
Source: PA
Source: PA