Having experienced playing in those conditions during his career, O'Gara feels attitude rather than altitude was the key factor in Ireland's late collapse in Johannesburg, with a winning position in their grasp.
And he worries Ireland haven't yet mastered the ability to string successive big performances together.
In his Friday Irish Examiner column, O'Gara writes: "Joe Schmidt and his players should and will be sick after Ellis Park last Saturday. Altitude? No I’ve played there. I don't believe that.
"Whatever happened, no one can dispute it was the biggest disappointment in Irish rugby in a long, long time.
"When you're 19-3 and 26-10 up away from home, with a first test in the bag, and history beckoning, we return to the achilles heel issue: is Ireland a once-off type of team? Schmidt is a Kiwi and they don't do moral victory. Those days are over for Irish rugby.
"South Africa are average but the confidence they got from the last 40 minutes will stand to them tomorrow in Port Elizabeth."
"The thing with Ireland is they have to get angry.
"These Irish players are so fit and so well managed that fatigue and altitude problems are not legit excuses.