The 35-year-old has enjoyed sustained success since taking the reins at City in 2013, winning six trophies including the Women’s Super League title in 2016 and two FA Cups.
But he will join men’s MLS team New York City in the United States as assistant manager after his final game in charge against reigning WSL champions Arsenal on February 2.
And after watching his team defeat Everton 3-1 to maintain their title push, Cushing stressed that the decision to move on from the club was a heartbreaking one for him to make.
“Wednesday was a difficult day and it was probably a bit of a shock to the team,” he said.
“People might have thought there might be a hangover or a bit of emotion [against Everton], but that group has shown how professional they are.
“I don’t think the time would ever have been right for me to leave this team. It’s been such a huge part of my life.
“I don’t define this team – it’s the players I’ve worked with over the years and the staff.
“We’ve developed a lot of young English talent and I’m proud of that. I’m proud of how many games we’ve won and how many trophies we’ve won.
“It’s hard because I don’t see myself walking away from this job but it’s a good opportunity and good for everybody that we continue to push the women’s team on.”
Cushing has been the club’s only manager so far in the WSL era and will leave City with 18 months left on his contract, having signed a three-and-a-half-year deal in December 2017.
He has overseen their rise to become a dominant force in the English game and with his team in the hunt for the title once again, he believes he will depart with the club in great shape.
“This team has a feel that we’ve never had in six seasons – there’s a different feel,” he said. “We’ve been so consistent. We’re winning games easily, scoring three and four goals.
“The likes of Janine Beckie and Caroline Weir and Pauline Bremer are hitting levels they’ve never hit in their career.
“The likes of Steph Houghton and Keira Walsh and Jill Scott are being as consistent as they’ve always been. If we beat Chelsea and Arsenal here, we win the league.
“I’d always be heartbroken about leaving this team because it’s been such a huge part of my life. It’s been far more than just coaching a football team.
“It’s not the perfect time but I trust the people at this football club. We want to be world-leading at developing players and developing coaches. This is the next step on my journey.”
And when he was asked to reflect on his greatest achievements while in charge of the Citizens, Cushing insisted that helping his players develop stands above winning silverware.
“Earning the respect of the players – people like Jill Scott, Steph Houghton. I call them friends now,” he said. “I’ve pushed them hard at times and they’ve pushed me hard.
“It’s earning the respect of the players and hearing them say nice things about me. It’s a testament to the hard work we’ve put in together.”