Synchronicity, intimacy and productivity
A shortcut to customer and co-worker intimacy is to respond in real time. A phone call is more human than an email, a personal meeting has more impact than a letter.
On the other hand, when you do your work on someone else's schedule, your productivity plummets, because you are responding to the urgent, not the important, and your rhythm is shot.
The shortcut analysis, it seems to me, is to sort by how important it is that your interactions be intimate. If it's not vitally important that you increase the energy and realism of the relationship, then insert a buffer. Build blocks of time to do serious work, work that's not interrupted by people who need to hear from you in real time, right now.
On the other hand, for interactions when only a hug or a smile will do, allocate the time and the schedule to be present.
Confusing the two is getting easier than ever, and it's killing your ability to do great work.