At every point in the prime of my career I felt an edge: a tension, a need to focus. I would be snappy if anyone said anything annoying to me in the lead-up to a game. My mum, my wife: they would all see the pressure I was putting on myself to stay at the highest level.
When that goes, a part of you dies. Those feelings will be familiar to Manchester United's players as they struggle to regain their form and calm the nerves of their supporters.
David Moyes' men are now in the position of having to play for their futures. As Sir Alex Ferguson used to say, there is nowhere to hide when 76,000 pairs of eyes are on you at Old Trafford. Those spectators know what good players are and they are accustomed to success. Weaknesses are flagged up right away.
The lives of some of these players will turn turbulent if they reach the point where they are moved on. The public perception is that the manager is under pressure and the players have a get-out-of-jail card.
But it does not work like that at a club of United's stature. There is no taking refuge behind the manager.
Eyes are on everyone all the time. That rule may not apply to West Ham, say, another club whose manager is in the spotlight, where the players can get away with having more bad games than you could at United. You play badly once at United and it goes in the notebook.
I think Moyes is in place for the long term, despite the present difficulties. If the players see it that way, then logically they will be playing for their own places. There is only one way to go after United, and it is down. They know Moyes could have only one reaction to a bad season - and that is bringing in new faces to make it his team. There will be casualties.
A lot of these United players now have a point to prove. If the board are behind Moyes, as I believe they are, then the onus shifts to the team to save their own skin. Moyes will be making judgements constantly.
This is a side who have lost a number of household names. Paul Scholes has gone and Ryan Giggs and Rio Ferdinand are playing less often. The old bedrock of the team is no longer there.
Attention moves from there to the next wave, and the question: are these lads good enough to play for United?
For some, this could be their only chance to become established United players. If they are sold, they will not come back. The fight now is to embed themselves in Moyes' plans. With each defeat the chances of them being there next year diminish.
For that reason, we should not underestimate the pressure the players are under. You may not see it as the public and media obsess about Moyes but I can assure you those anxieties will be surging through the dressing room.
Wayne Rooney, Robin van Persie and now Adnan Januzaj are fixtures. Nemanja Vidic still does a very good job and will not be going far. Danny Welbeck is another with a solid future.
Michael Carrick also looks secure. Others, we may have seen the best of, and the task for them will be to hang on for as long as they can.
But they need a new wave to carry Manchester United forward: the likes of Chris Smalling, Phil Jones and Tom Cleverley, who have to get in the team and prove their worth.
Welbeck is half a step on from those three. Cleverley is often judged harshly for not being a Paul Scholes. He is a different type of player. He brings industry and steady passing. More than any of the players under discussion, he will need a thick skin. If he comes through this, he will be a lot better for it. It is a tough time for Tom's generation.
Beyond them, Nani, Anderson, Antonio Valencia and Ashley Young are in that group between the youngsters and the ageing legends. They should be the mainstay of the side. They have been around a while, are accustomed to success but also have a few years ahead of them. The same test is applied to them: which of them is good enough for the trials ahead?
The first big change has been the manager and the second is results, so it is easy for people to draw a line of cause and effect. Suddenly it looks like Moyes' fault. But the longer it goes on the more deeply people will look into causes beyond the manager.
There will be a microscope on every player.
When they start to feel beleaguered and undervalued, then another level of difficulty kicks in. That is where we are heading.
Players at the middle-range teams can escape the storms that affect those at the top six clubs. The fear of failure, of demotion, is much sharper.
If there is not much difference between being seventh or 11th in the Premier League, then life can seem a lot less pressured. The top players are looking down at the rest of the pyramid and have more to lose when they fall.
Manchester United players have a lot more to fear and the ability to use that pressure constructively is part of what sets them apart.
Their squad remains packed with born winners to whom losing is alien.
In defeat, the hurt runs deep. The terror of losing is one of the biggest drivers at the top of sport; plus the fear of being told, "You're not good enough". This bad run United are on will be hurting the players more than it would at a lesser club.
I see it as a confidence drop. I have watched their last three games and at no stage was the performance shocking. They played well against Spurs but got beaten. They were on top of Swansea for most of that match. The same applies to the Sunderland League Cup tie. They are not the Manchester United we expect but nor are they a disaster. When that self-belief returns, they will be back to winning ways.
There is a lot of talk about players being mollycoddled these days but you have to have that edge I talked about all the time. If you dip five per cent at this level you're a gonner. Daily Telegraph