The Dons took the lead just four minutes into the first half when Joe Lewis met Jake Reeves’ swinging corner and headed past Matt Cox.
AFC Wimbledon suffered a 5-2 defeat to Premier League side Brentford in pre-season on Saturday afternoon at Plough Lane.
The Bees equalised in the 22nd minute when Igor Thiago latched onto a ball just inside the area and fired past Crystal Palace loanee Owen Goodman.
Brentford took the lead nine minutes later when striker Thiago doubled his tally with a chip over the onrushing Goodman.
Yoane Wissa added Brentford’s third from the spot when Huseyin Biler brought down the striker inside the area.
Kevin Schade came on at half-time and scored Brentford’s fourth when he raced past Wimbledon’s defence to knock beyond substitute keeper Lewis Ward.
Bryan Mbeumo made it 5-1 with 15 minutes of normal time remaining.
Matty Stevens got his first goal for the club since signing from Forest Green in the summer when he steered James Tilley’s cross past Brentford stopper Hakon Valdimarsson.
“For 25 minutes to half an hour, we were the better team – we were really good,” Jackson told the South London Press.
“We took the game to them. We pressed really well and counter-pressed really well.
“We should have scored at least two – maybe three.
“There was loads to like. But against a team such as this, you only have to switch off for a minute and you find yourself down.
“We went in 3-1 down at half-time, but we could have been two or three up.
“That shows the levels.”
Biler, who gave away the first-half penalty, was sent off two times last season.
The 22-year-old penned a one-year extension this summer after his deal expired.
“I want him to learn from days like to do and improve,”
“He has so much talent and ability, but there is lots to learn.
“Days like today, when you get in those moments, you can’t be that rash.
“In a league game, that could certainly be a yellow card – maybe a red.
“But this is why we have these games. I want the boys to make mistakes trying to do the right things, and take the learning from it.”