Carla Ward said it was "devastating" telling her Birmingham squad that she was leaving at the end of the season.
Ward took over in August last year and secured her side's place in next season's Women's Super League, despite having the smallest budget in the division.
Her resignation was announced on Friday and she revealed it had been an emotional moment when she informed the players.
"I came in here quite strong this morning to tell them and I had it pre-rehearsed in my head, what I was going to say, and I must admit, I don't cry in front of anyone, but after the first two words, yes I had a complete meltdown, it was horrible," Ward said.
"But I think it probably sums up how I feel about the group. It was devastating to share that with them, because we've stuck together this year, it's been tough, and they've been unbelievable.
"I'm not going to lie, it was really tough. I'd be lying if I said it wasn't emotional from everybody in the room. Ultimately, the time was right to be stepping away."
This season has not been without its challenges, with City's squad sending a letter to the club's hierarchy highlighting a lack of support for them compared to that given to the men's team in April.
The complaints were reported to include players earning less than the minimum wage, delays over treatment for injured players, a lack of access to the training-ground gym and changing rooms, and travel arrangements for away fixtures, prompting a statement from Birmingham saying the club was committed to the women's team.
"It's something I've been thinking about for a couple of months, it's been an unbelievable year, it's been an emotional year. It's been tough at times," Ward said when asked about the reasons behind her decision.
"But it's been an opportunity that I've loved every minute of. I believe I've given absolutely everything I've got and I believe now it's time for a fresh chapter."
She added: "The finer details will always be kept in house and rightly so, and one thing is I will say is I'll be forever grateful to the Blues for allowing me to step into this division. I've worked with an exceptional bunch of individuals that have given everything.
"Ultimately, what we've done this year I don't think is sustainable mentally and physically and I think by stepping away and allowing someone else to come in... I think that that's important because ultimately, number one is it's got to be about Birmingham City staying in the WSL."
Ward will see out the season as manager and will be in the dugout for her side's FA Cup fifth round clash with Southampton on Sunday.
