There's always something strange about bumping into an ex. Sometimes it can be satisfying -- perhaps they're looking a bit shabby, or have obviously fallen on hard times.
Maybe they've shacked up with someone new who, frankly, isn't much of a looker. Other times the reverse is true -- it's that day you're late for work and haven't had time to shower, or maybe the time you've had a drink too many and end up saying something embarrassing.
But most confusing of all is when, in spite of the knowledge of everything that went wrong in the past, that surge of mutual longing just wells right up again. Before you know it you're meeting for a drink and, well, you know the rest.
The problem for Chelsea, as for any serial daters, is that their exes are simply everywhere.
After rattling through 10 managers in 10 years, barely a month goes by without some awkward encounter to set the mind wondering what might have been.
Of course we all know what happened this summer. Fresh from ending a relationship with Rafael Benitez that, while doomed from the start, seemed to be developing into something a little more substantial, Chelsea were confronted with the newly single big love of their lives.
We've all seen it happen: two people who seemed so perfect together, but parted in haste, and suddenly they're both available.
The outcome is inevitable, and so it was at Stamford Bridge. Jose Mourinho moved all his stuff back in, started re-arranging the furniture and publicly re-affirming his undying love for the blue part of west London.
Now here we are, barely six weeks into the new season, and this time around it seems a little different.
Mourinho is as suave as ever, of course; witty press conference quips and a debonair touchline demeanor go a long way to making everything in the garden look rosy. But there's something oddly listless about his team.
To begin with, there's the question of the midfield. Juan Mata, the darling of fantasy football league managers everywhere, has been the lynchpin of so many good things about Chelsea since he signed; but from the moment Mourinho took charge the former Valencia maestro's place has looked in doubt.
Meanwhile, fellow attacking midfielders Oscar and Eden Hazard, while outrageously gifted, seem to pose more questions than answers.
How do they play together? Do they have the physical stature to impose themselves on more abrasive opponents?
Add in the return of another attacking midfielder, the exciting Kevin de Bruyne, loaned out successfully to Werder Bremen last term, along with the addition of buccaneering wide man Andre Schürrle, and there is a wealth of riches in the middle of the park.
Odd then that Mourinho chose to gazump one of Chelsea's most recent and perhaps bitter exes, Tottenham Hotspur boss Andre Villas Boas, and divert -- you guessed it -- yet another attacking midfielder, Willian, to Stamford Bridge.
How to fit any combination of these together into a usable whole, not least in the mayhem of England's rough and ready Premier League, is quite a conundrum. Right now Mourinho's first choice midfield is anyone's guess.
Then there's the front line. The football jury returned a verdict on Fernando Torres some time ago, and few would describe his time at Chelsea in anything more than tepid terms at best.
The fact that Mourinho has kept him on may owe more to an absence of realistic suitors than a desire to be the one who finally made things work with the Spaniard, but keep him he has.
Demba Ba has also struggled somewhat since joining from Newcastle, but while reports suggested he might have been off elsewhere, possibly to Arsenal, he has also stuck around.
Romelo Lukaku, another fantasy league favorite after a prolific season at West Bromwich Albion, seemed like the kind of rough diamond, with more than a little of Didier Drogba about his physique, that Mourinho could make shine.
But after an agonizing missed spot-kick at the end of 10-man Chelsea's spirited Super Cup final defeat against Bayern Munich, he will now be lining up in the blue shirt of Everton this season. With another former Chelsea man, Daniel Sturridge, setting Merseyside alight with his goals, it seems odd to let such potential go.
Competitive Premier League
Then there was the pursuit of Wayne Rooney.
Yes the Manchester United striker had frustrated former boss Alex Ferguson and needled his club's own fans more than once with his apparent desire to flee Old Trafford, and new manager David Moyes offered mixed messages about the forward's future.
But there always seemed something slightly implausible about the idea of the Red Devils letting Rooney join one of their title rivals.