Agree, except instead of asking about nearby short-term stuff that doesn't really matter, ask about your largescale beliefs, plans, and values, for at least a few years straight. Chances are good your whole life's been a lost purpose. And if not, it'd be nice to know for sure that it hasn't been.
Rationalist mindfulness seems potentially harmful if your designation of rational has some affective judgment baked in, which it probably does. Normal mindfulness meditation is probably better. Mindfulness itself brings spiritual (and cognitive/neuronal) transformation.
No, I'm suggesting that you do focus on the short-term stuff, like sitting in a way that strains your thigh. Try it. See what happens.
At today's meetup in Tortuga, we were supposed to discuss something we're currently being irrational about. In retrospect I could probably have done better than the item I picked (for example, it now occurs to me that I'm probably currently being irrational about bedtimes and sleep-cycle stuff)...
But the key point is that while straining my brain to think of something I was currently being irrational about, but hadn't fixed yet, I noticed myself being irrational in small ways too.
For example, I was sitting on the floor in a way that was beginning to strain my left thigh, but wasn't standing up and finding a chair...
So I stood up and found a chair.
I think it might be a valuable exercise to spend an hour practicing rationalist mindfulness, constantly asking yourself, "What am I currently doing that is not rational?" as though you had to find something to fulfill your obligation to an LW meetup.