Johnson played 73 Tests, 153 ODIs and 30 T20Is for Australia.
Johnson, who played his last international match for Australia back in 2015, stayed a further three years for IPL and BBL commitments.
The 38-year-old spoke quite courageously of what he has had to endure during the filming of Channel 7's 'SAS Australia'.
"I've found it tougher since retiring from cricket," Johnson said. "All of a sudden, you're not doing as much. You sort of lose your purpose a little bit."
"I struggle with, probably, confidence at times. I'm in that transition now where I've been out of playing cricket for about two years," added the speedster, who took 313 wickets in 73 Tests, including an unforgettable run during the 2013-14 Ashes, and also featured in 153 ODIs and 30 T20Is.
To an obvious query whether he has found life after cricket very difficult, Johnson said: "Yeah plenty of times. I found out I've got depression … but I think the depression was something I've had even from a younger age."
"It [cricket] sort of blocked things out in a way. It sort of hid the depression, but there was a lot of times where you would go back to your room, you're away from family and you start to dwell on things."
"Through my cricket career, I actually just dealt with it [depression]. It's just about me now actually moving forward and taking it upon myself to be active with certain things, to keep my mind going," he added.
Living the life of an international cricketer under constant pressure to deliver, especially on long tours away, may have also taken its toll, feels Johnson. He recalled the 2011 South African tour to stress home this point. The series came on the back of a home Ashes defeat, where he had been constantly mocked by the Barmy Army.
Johnson admitted it reached a "point where I wasn't enjoying being a professional cricketer" and he "took everything personally".
"You have your moments where you struggle with it really bad and it can be tricky when you've got a lot of time to think about things," Johnson said.
"You've just got no control whatsoever and your mind starts playing those tricks on you, you start thinking of the worst."
(Inputs from ESPNcricinfo)