io9:

People spend 46.9% of their waking lives thinking about something other than what they’re actually doing. It’s a terribly inefficient use of one’s mind and, worse, it actually seems to make people unhappy.

Letting your mind wander might seem like a bad thing, but really it’s just the natural byproduct of being capable of abstract thought. Humans are capable of thinking about things that have happened, things that might happen, and things that may never happen at all. (As a science fiction blog, we rather encourage doing that last part.) Sure, letting your mind wander is a good recipe for goofing off, but it’s also a necessary part of contemplation and reflection.

I’ve quoted this from Auden several times before, but it just sums it up so perfectly:

With envy, terror, rage, regret,

We anticipate or remember but never are.

But yeah, I think there’s maybe a little more nuance to this. As many have said, especially Buddhists, the future and the past are mere abstractions. We only actually exist in “now”. Alan Watts used the image of a ship’s prow to symbolize this — we only ever exist right there, at the prow, as it cuts through the water, and the past flows behind us in our wake.

If you spend every present moment wishing you were somewhere else, you’re going to feel perpetually dissatisfied, since the pleasures you’re so eagerly anticipating will seem boring once they become actualized, and you’ll already be looking forward to the next one. It’ll never feel like you’ve actually experienced anything fully. You’ve become attached to the wanting, not the having.

But on the other hand, meditation is, in many ways, a form of purposely letting your mind wander, tiring itself out. Personally, I do my meditating while listening to music, and I find it revitalizing, not distracting. It’s like a mental equivalent of a good workout. Sometimes I do it while performing simple tasks that don’t require my undivided attention, like washing dishes or cutting grass, and it seems to me that somehow, the repetitive physical activity keeps me grounded, even though my mind may be on various other things. I’m not sure how to explain that exactly.