first impression

The first impression is vitally important for referees at all levels of the game. When arriving at a ground first impression can sometimes help to reassure frustrated team officials, pubescent teenagers and their dedicated parents who are mentally participating in the game on the sideline. 
Arriving at the home club, greeting the involved team managers and club secretary, asking for your dressing room, determining when you are going to check the team sheet and match balls - makes a lasting impression for your later performance.
Arriving at the ground too late, wearing sloppy sweatpants and nike airmaxes e.g. demonstrates a certain attitude to the game you are going to handle. Arriving in-time, being mentally alert, having chin up and chest out, being friendly and politely as well as wearing normal/professional clothes can however show respect from the first moment or impression on. And this might have an effect on how much respect is shown to you on the pitch.

And even on the field of play, the same counts. Your first whistle, its intensity, length, maybe even your gesture at the kick-off can contribute to a determined, authoritative, generous first impression – just in accordance with the approach and message you want to send. 
If you split a football match into two halves, it is pretty likely that you remember the first and last minutes of each half better than the middle of both halves. That’s also due to the mere circumstance that specially the first moments in the game are important for the way a match takes from the referee’s perspective. The first impression counts. Mistakes and systematical weaknesses in the first or last 15 minutes might be more painful for the referee’s mark than problems between minutes 55 and 70.
And sometimes, normally (= illogically) thinking humans go a step farther: Once we have established a first judgment, we often subconsciously seek pieces of information that are congruent to it. This is known as the so-called confirmation bias. If we think that a referee has started poorly, we tend to be more sensitive to mistakes and weaknesses later on in the match – our perceived reality is blurred.

Take Home Messages:

1)      The first impression counts. There is no second chance for a first impression. If you are a referee, be aware of that. The way players and officials perceive you in the first moments of the game (body language, whistle language…), but also BEFORE the game (politeness, self-presentation, outward appearance), has a huge influence! 
2)   Maintain your concentration levels throughout the game - if it helps then mentally break the game up into 10 or 15 minute intervals. Self assess your performance and make the adjustments to your game. Try to get into the habit of starting the game as you mean to continue. 'Avoid being a Jekyll and Mr Hyde.'
3)      The last impression is not less important. Keep your concentration high until you leave the ground!