That was part of a contrite statement which the 47-year-old issued through his solicitor, Richard Brooks of Withy King.
The British Horseracing Authority had used much heavier language on Wednesday when it accused Butler of an "appalling" dereliction of his duties, announcing that the Group One-winning trainer admitted to all seven charges against him relating to samples of an anabolic steroid found in horses in his care.
Nine of his horses produced positive samples - five cases of which were identified as the joint treatment Sungate, which contains the banned anabolic steroid stanozolol. The BHA, however, considered Butler's admission of administering another substance, Rexogin, to four horses himself to be even more serious.
Rexogin is designed for use in humans, often for bodybuilding, and contains 10 times as much stanozolol as Sungate.
Butler's statement read: "While this has been a devastating and humiliating experience for me, I am above all aware of its impact on others: not just my family, staff and owners but also the sport I have always loved. I have no intention of hiding from my responsibility for an error of judgment that has undone many years of honest endeavour.
"I must emphasise that no harm resulted to any of the horses involved and, above all, I would never have knowingly risked any such harm. It was wrong for me to cut corners but I did so principally through naivety. I have made a big mistake, and am paying a big price.
"All I can do is try to pick up the pieces. I will do so with a painfully renewed sense that the principles I neglected, in one disastrous lapse, will be those that serve me best in trying to rebuild my life."
The BHA also announced that owner Stephen Arnold has been disqualified for three months after admitting to breaching the rules in relation to laying 10 of his horses.
Arnold, whose horses run under the moniker of Rakebackmypoker.com, was charged with 10 counts of laying his horses to lose, involving races between June 2012 and March this year. The owner, who has moved 21 of his horses to the Southwell yard of Ann Stokell recently, later wrote on his Twitter page: "Huge thanks for all the support I have been shown in very difficult times. Disappointing to get a ban, but at least I can lease the horses to stay in the yard with Ann Stokell and no staff will lose their jobs so I am happy about that as that was a big worry for me."