Sheerin, 47, took charge of 23 competitive matches last campaign, winning only eight of them.
He departed the club in December after his side lost 6-0 to Queen’s Park at Firhill in what was one of the club’s worst-ever results.
Falkirk eventually finished sixth, a whopping 35 points behind champions Cove Rangers.
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“I lost my job due to my own inadequacies,” Sheerin admitted to the Herald. “For a club of Falkirk’s stature, you have to get better results than what we did up to that point of the season.
“The Queen’s Park match made the board act and I understand that because the manner of the defeat was so comical, but a manager needs time.
“We would have lifted the group after that. It was just a step too far at that point for the group.
“I really wanted to get to the January window. We had targets in mind and people who would have really fixed those problematic areas.
“People keep changing things all the time at the club, and I think what they really need is stability. Those in place now need to be given time to get it right. The process of building a team and a way of playing takes a long period of time.
“Looking back, I am man enough to admit that the defensive deficiencies and the lack of goals just weren’t good enough.
“The way I wanted us to play should have been much more fruitful.
“I don’t think I ever lost the group of players. I can say that with confidence.”
The former Aberdeen assistant coach also believes he made an error letting forward Anton Dowds go out on loan to Arbroath at the start of his tenure.
He went on to be a key factor in Dick Campbell’s side climbing to the top of the Scottish Championship while Sheerin’s Falkirk side struggled to score goals.
“I was rash with some of the decisions that I made,” he added.
“Anton Dowds was a big one for me and one I do look back on. Stripping everything back in hindsight, it was the wrong thing to do.
“He was a little bit different from the other strikers we had at the club. I was probably too quick to make that call.
"Anton proved that because he was excellent on loan at Arbroath and when he came back.
“Monday to Friday in training, potentially I was too intense with the group in terms of their working, but you could strip back everything, you could go on and on.
"As a manager you live and die by what you do and I made the decisions at the time because I felt it was right.
“I didn’t want to be a failure at Falkirk. It really hurt.
"Maybe I was inexperienced in the eyes of some of the support but I have been in the game a long time.
"I have worked with one of the best managers in the country in Derek McInnes for eight years.
“The first set of matches weren’t good enough.
“But I believed in the style and we were only in the club for five months, we were still in that period of bedding in our ideas.
"When I left the club were only nine points away from top spot and three from the play-offs.
"There was so much football to play.
"It was just one of those seasons.
"I wish Falkirk all the best and I really hope they can kick on now.”
Sheerin is now working as a coach at Kilmarnock, once again working under boss Derek McInnes. He joined the Rugby Park club last season after a short spell out of football.
"I’ve really enjoyed it so far. It is an important time for everyone at the football club,” he said.