The Reds were poor in the first half and trailed to Jamie McGuire’s 39th-minute goal before Seamus Conneely scored two minutes after the break and Terry Gornell fired home a 71st-minute winner.
Victory means Stanley finished in 17th place with just two wins in their final 14 games quashing hopes of finishing higher.
“It was two contrasting halves which summed up our season,” said Coleman.
“In the first half we were diabolical and I told them at half-time it was unacceptable. The fans pay their money and deserve better.
“There were a lot of words said at the break, we looked insipid and we were rubbish but then, in the second half, we had them on the back foot, scored an early goal, which also helps, and then finished strongly.
“I don’t know why we didn’t play like that for 90 minutes, but we have been too inconsistent this season which is why we finished where we are.”
Mansfield boss Adam Murray, who took over in November, was similarly underwhelmed as his side finished in 21st spot.
“I have never wanted a season to finish as quickly as this one,” said Murray, who at 33 is the youngest manager in the Football League.
“Now we have got to be positive and look forward to the future and start planning for next season.
“I have made decisions about players over a period of time and again here we showed our weaknesses.
“We took the lead and were strong in the first half, but then we haven’t been ruthless when we’re on top, which has happened all too often this season.
“The last six months have been a massive challenge.
“We knew in pre-season that it would be a fight and so it has proved and we have paid for our inconsistencies.
“We have had a lot of bad luck along the way and now we just want to look forward.”
The first half was largely one to forget before McGuire got the ball on the edge of the area and volleyed home his first goal of the campaign.
Stanley had that half-time blast and, in the 47th minute, Josh Windass’s initial header was saved before Conneely followed up and fired home his third goal of the season.
Stanley then upped the pressure and the winner came when striker Gornell raced down the left wing and put the ball past on-rushing goalkeeper Lenny Pidgeley to seal the Reds’ victory.