Roy Keane reaches his 100th match in management today and, in a manner that typifies such a relentless, driven individual, anguish is a more likely response than celebration. Half-measures do not apply. As he surveyed his 27-month spell at Sunderland, during which the club have been transformed beyond recognition, the Irishman’s self-appraisal was brutal. “Could do better,” he said.

Milestones have always been millstones for Keane, but given the extent of his impact on Wearside — from languishing at the foot of the Coca-Cola Championship in August 2006, Sunderland now have designs on Europe — reflection is important and perspective necessary. Keane may appear a serene figure in the dugout, but he is not immune from the stresses of his profession.

“I’m 37 years of age and in my first job and it’s been tough,” he said. “But I didn’t think for one minute it would be easy. I’ve been a manager for two minutes and I constantly look at the mistakes I’ve made. That’s part of management, part of the game. Whatever the punters thought last weekend when we lost, multiply that by a thousand for what was going through my head.

“I’ve always been like that and that is possibly why I will be a manager only for a short time. Maybe that is what held me back for certain parts of my football career, being overly critical of myself. Speaking to other managers, they find a way of doing something off the pitch. I might need to spend more time with my family because the management business is very much in your head. It affects your sleep, your appetite.

“I was always impatient as a player and I’m the same now, but maybe other managers have a different way of switching off. When I was a player I got over it by going out and socialising. I’ve tried golf, but didn’t like it. Some managers go horse racing or watching games all over Europe. That doesn’t appeal to me. I suppose I could go to the opera, the arts, wine tasting or something like that. Fishing.

“Going to the movies with my kids, walking the dogs, lunch with the wife, that is still a good switch-off for me, but switching off on a Sunday after a defeat doesn’t happen. That’s normal — as a manager, you shouldn’t be getting up and having fried eggs and black pudding if you lose. I always go to mass. Win and you say ‘thank you’, lose and you say ‘give us a result’ and put an extra 20 quid in the tray.”

Keane, who is negotiating an extension to the contract that ends in May, has won 42 and drawn 17 of his century of fixtures, losing 40. “We have lost too many games, far too many,” he said. “But the important thing for any manager is from the day you walk in to the day you leave the club is in a better position. The expectations are higher — that is something I have done and that gives me great hope.

“You want to see the club make great strides. If I wake up one morning and think I can’t improve things, then it is time to leave. You can improve all the time. But it takes time and I can be as impatient as the next man. The beauty of football is that tomorrow is a new day and a new challenge for us. That is sport and that is life. I want my team to be known as a good passing team and hard to beat.”

Keane has either bought or moved on more than 100 players at Sunderland, but his squad remains bloated. “The only activity in January here will be players going out,” he said. “Sometimes you try too much too soon and maybe that is the case. I have brought too many players to the club because I want us to get to the next level, but there comes a point where you have to say enough is enough.”