His age is a bit of a factor, but having his name brought up in every trade talk doesn't help with his state of mind, wondering whether or not he'll still be a Celtic when he wakes up every morning.
He may say that he understands about the business side of it, but this is a guy who has very few peers when it comes to having played for the same club his entire fourteen year career.
Those kind of roots go deeper than most of us can understand, and to have that up in the air all the time can have a huge effect on the psyche, no matter what anyone says.
He'll be a different guy after the trade deadline, one way or another, and I personally hope it's as a Celtic ... until he retires.