Why is this?! Assuming this ability is universal (and not just something chime and I are good at:), there must be an innate psychological reason. Possibly even a "simple" reason.
I will venture a guess: real or imagined self-threat is always associated with failure to complete a "work" task. This is never true for an individual "play" task.
Thoughts?
The reason I break it down into two is because of how I look at tasks with respect to stress. Nearly every task either adds (even if slightly) to my stress or relieves it. Very few are on the border and if they are on the border, I'd say they add to my stress just because they're not actually relieving it. My goal is to mix it all up in a healthy balance that best suits my personality.
You say: "Nearly every task either adds ... to my stress or relieves it." My question is: why does this seems to be true for everyone?
The answer is not necessarily related to energy or time expenditure. For me, playing consecutive games of intense full-court basketball is fun/relaxing/play.
The Stephen Covey's method ("7 habits" fame) specifically deals with this issue. I highly recommend you to read the book "First Things First", but basically it's about scheduling the big stuff first (literally blocking chunks of time in the calendar), and only deal with the today/soon/whenever tasks on the remaining time. It's not as simple as that, you need to read the book to actually apply it effectively, but I can tell you that I've been following it at least for the past 5 years and it has been extremely effective for me.
I'm going to build something simple around this idea for our office.
Off topic: Oddly enough, I looked at the info about you and have actually run into your site before through your other project Sched. Cool personal page. I actually emailed yesterday regarding the Developer API on there to see if we could use it on our music festival site. Hope to hear back!
Does it have an API? Being able to use it easily from a cell phone app would make it perfect, and I've been looking for a project to learn the Android SDK.
If you really want an API or even a secure RSS feed, let me know and I'll see if I can set something up.
I wrote a super simple webapp http://untodos.com/ (mostly for myself) that is pretty much the opposite of every time/schedule management app out there. I don't care about the preciseness of the tasks, I care about the priority. Inside my mind, I can't visualize 4:15pm-5:45pm Friday next week. The only time horizons my mind intuitively understands are today, soon, and whenever. My app and now my life is designed around that principle. After years of being burdened with feeling stressed and overworked, I think I finally have a handle on my busy schedule now and I know my stress is much lower.
My biggest gripe with traditional time management method is that you lose sight of the big picture and only concentrate on the small urgencies. We forget the important due to the urgent. If writing a book is one of your life goals, where does it fit on a calendar? I know where it fits on mine, in the "whenever" section. Once a day, I go over my "today", "soon" and "whenever" sections and move things around as I deem necessary.
I feel my view of managing my time is more encompassing than compartmentalizing. I am one person, I don't want "buy groceries" on a separate list from "meet clients" because both happen within hours of each other anyway. My life is one life, why have separate types of calendars and events. I thought deeply about what actually matters to me and realized that all I care about a task is whether it is "work/chore" or "fun/relaxing." As long as I have a bunch of fun tasks interspersed between my regular chore todos, I can manage my time well.
I guess the key lesson about time management is that you have to know yourself and figure out what works best for you. For some, it's Outlook, for some it's GCal synced with iPhone using RememberTheMilk app merged with iCal feeds from your fridge. And for some like me, it's just a no-deadline, no-reminder list of tasks with varying priorities. Find what works for you and grow with it. And if something doesn't work, don't blame yourself and personalize the stress as being caused by your inefficiencies but rather seek a system that fits your personality.