The fiery Italian admitted after Saturday night's 1-0 defeat to Manchester City in the Barclays Asia Cup final he had been driving his players hard.
Di Canio is of the belief the Black Cats had it too easy under Martin O'Neill, to the extent some of his squad were "under trained".
There is no chance of that happening this time around, with Di Canio imposing a punishing schedule on his squad, who now head for home ahead to continue preparations for the opening Premier League fixture with Fulham on August 17.
But Gardner is not bothered as that is just the way he likes it.
"It is tough, I admit it," said the 26-year-old. "But it is a good tough because training is hard. I am a firm believer that the attitude to training should be the same as it is in life generally.
"If you work hard in life you get a good life. That is what we are doing as far as training is concerned, so hopefully we will have a good season."