The Chelsea forward has been included in the Lionesses squad for next month’s home tournament despite not playing for the Blues since February.
She struggled with extreme fatigue and had an oxygen tent installed at her home to aid her recovery to ultimately seal a place in Sarina Wiegman’s squad.
“I wouldn’t say there was fear, I never really had in the back of my mind, ‘oh my God, I’m not going to get selected for the Euros now’, because I just wasn’t focusing my energy feeling like that,” said Kirby, who was an unused substitute in Chelsea’s FA Cup final victory over Manchester City last month.
“Going into Chelsea to training, I had conversations with (manager) Emma (Hayes) and just said, ‘look, what will be will be, if I’m ready I’m ready’.
“I’m a believer that things happen for a reason, and either I’m going to be part of the squad or I’m not. If I show, and I don’t get picked, then at least I know that I’ve done everything.
“There was definitely relief to get selected but I don’t think it was a case of thinking about it every day because it’s not in your control, it’s as much as you can do.”
Kirby has been dealing with the issue for around five years and has learned to listen to her body.
Her first minutes since February were as a substitute in last week’s 3-0 win over Belgium at Molineux and she could feature in Friday’s second warm-up game against the Netherlands at Elland Road.
But she admits it can be difficult to handle having been unable to pinpoint the source of the problem.
“It was extreme fatigue and extreme exhaustion. There was talk about underperformance fatigue syndrome, so there were loads of things that were getting chucked out here and there,” said the 28-year-old, who has 15 goals in 54 caps.
“It wasn’t like you have a brain scan to show you’re dealing with a certain thing, so it was a lot of working with different psychologists to learn different ideas, working with different specialists in terms of nutrition and the recovery.
“I got an oxygen tent put in my house, so I was just learning different things that can help and it’s opened my eyes in terms of not just the recovery you may see, it’s the other aspects that go alongside it.
“Throughout my career I’ve been learning many different things with my journey.
“That is a concern (being unable to find the definitive issue), but for me I am learning each time. This is something that I’ve dealt with probably for five for six years of my career, it’s not something that just happened in February.
“It’s been an ongoing feeling that I’ve experienced, so I’ve kind of learnt now what the triggers are, when I start to feel a certain way and how I can prevent that from happening.
“It’s not something I can control. It’s sacrifices that I have to make and decisions I have to make.
“It’s definitely opened my eyes a lot more in terms of it’s really important to listen to your body and when you need to take a break, you take a break and really benefit from it.”
Kirby has also had support from boss Wiegman and revealed the confidence her manager had in her, having made the grade during training at St George’s Park.
“It’s more relief for me. It’s been a journey, especially these last few months, but I think as soon as I started to feel better, I was training every day with the mind of being ready for when Sarina announces her squad,” she said.
“It (selection) was one of those when you’re sitting there waiting for your phone to light up to say, ‘go to the room’, a bit like X Factor.
“I walked in and I saw her smiling, so then I was like, ‘OK, hopefully she’s not smiling and sending me home.
“She told me that she knew all along that I was going to be an important part of this team, and we had some really honest conversations leading into it.
“I said to her, ‘I need you to be honest with me and I’ll be honest with you, if we both feel like I’m not ready, then we make that decision’.
“Obviously it was a good conversation and she could see in the two weeks going into the Euros that I was growing in the team, and I was in training and I didn’t really feel like I’d been away, so that’s always a nice feeling.”