This is not an easy letter to write, but things just can't go on as they are. Seeing you look so pained and hurt during Arsenal's 3-0 defeat against Manchester City on Thursday night -- not the 3-0 defeat at Wembley, the 3-0 defeat at the Emirates ( I know it's difficult to keep up with them all nowadays) -- was a moment that will live with football lovers forever.
Because it is not just Arsenal supporters who are finding it so tough to watch at the moment. Everybody is hurting now, Arsene.
You are the man who turned a struggling, famous old club into one of English football's best-ever teams. But if you are not careful, you will end up taking Arsenal back to where you found them.
You changed the way we looked at football in England. When Sir Alex Ferguson dismissed you as some unknown who had "just come from Japan" shortly after you arrived at Arsenal in 1996, we all laughed and privately agreed with the Manchester United manager.
But you proved him, and everybody else, wrong. You wiped the smile off Fergie's face, especially in the 1997-98 season, when that fantastic team of yours won the Premier League and FA Cup double.
What a team it was: David Seaman in goal; Tony Adams and Martin Keown at the heart of the famous back four; then the incredible partnership of Patrick Vieira and Emmanuel Petit in midfield. There was Dennis Bergkamp, Marc Overmars, Nicolas Anelka and Ian Wright up front, too.
It was a team that raised the bar, but you lifted it even higher by adding the likes of Sol Campbell, Robert Pires and Thierry Henry, who played such a huge role in Arsenal's 2003-04 "Invincibles" becoming the only team to win the Premier League without suffering a single defeat.
You had already changed the whole mindset of English football by that point, making players realise they were athletes who had to look after their bodies, on and off the field, but the style, grace and power of your Arsenal teams back then was a joy to behold.
There was a banner which the Arsenal fans displayed at Highbury, which read simply, "Arsene Knows." You did know, Arsene. You knew before everybody else, you knew how to make a team so devastatingly brilliant that it seemed as though nobody could stop you.
So forgive me for being blunt, but where did it all go wrong?
Ok, the move to the Emirates in 2006 hurt your ability to buy the best players, and keep them out of the clutches of rival clubs, but something changed when you left Highbury and you have never been the same since.
You became fixated with playing beautiful, eye-catching football, but you would never see the fatal flaw which tripped your new team up time after time. The steel of your best teams was replaced by flair, but you need both, Arsene.
When the going got tough for Adams, Keown, Bergkamp and Henry, they got going, but you always suspected that the likes of Cesc Fabregas, Samir Nasri, Laurent Koscielny and company would fall short when the chips were down.
And so it proved, but for some reason, you replaced like for like, refusing to compromise your principles. Yet the holes left by the departures of Campbell, Vieira and Henry were never filled and remain a problem to this day.
While you were looking for some kind of football perfection, Pep Guardiola was fine-tuning it with Barcelona and then Bayern Munich. For his City team to humiliate you and your Arsenal side twice in the space of four days, playing the champagne football which was one of your hallmarks, must have hurt.
This City team plays like your "Invincibles." You had the secret code, but somehow, you lost it and look where you are now.
Your team is playing in front of a half-empty stadium, with supporters booing your players off. Your position is under daily scrutiny, from supporters and former players alike -- the players you turned into heroes and legends.
Some say you should be treated with greater respect. You have even said it yourself. But football is a brutal business and the past is a stranger to those who only want success yesterday, today and tomorrow.
And this is the problem, and why you must accept that your time is up.
This current team of yours will not win the Premier League title this season, next season or the season after. Too many players are not good enough and your tactics, quite frankly, do not work in the modern game.
Everyone (with the exception of a few thousand Tottenham or Chelsea supporters perhaps) appreciates what you have given to English football, but your legacy is being tarnished with every defeat.
You should be remembered as the man who made Arsenal invincible, who saved the Premier League from a decade of United dominance, but all those positives are being washed away by a tide of negativity and acrimony.
The longer you stay, the worse it will get.
You are better than that, Arsene. For your sake and for Arsenal's, go.