It's commonsense that motivation comes before action; but in reality, action comes before motivation (where motivation is the feeling of wanting to do it; you can decide to do something whether you feel like it or not).
Some argue that this applies to other feelings, even to love; that if you act as if you love something, then the feeling of love will follow: love is a verb. Here's a striking clip from Paris Je T'aime that demonstrates it (though not, of course, proves it): http://www.youtube.com/watch?v=gIa0454xfyI
People often ask me how I manage to stay vegan (especially as I travel a lot). The answer is simple I don't need will-power all day I just need it for the 30 seconds when I'm ordering a meal or shopping for food.
I used to be a personal trainer, and the saying goes that 99% of getting in shape is just showing up to the gym. Once you get there, the exercise is easy and usually fun.
You'd be surprised how many people have equipment at home, but never use it. There's still required the equivalent move of "going to the gym", that spark of motivation/movement to get one's ass off the couch.
I can usually argue with myself to get motivated. The problem is when I cheat and pretend I already had the internal conversation and decided not to bother.
Seems to me that this is what the GTD Weekly Review is all about - you take stock of your world once a week, decide what is important and then spend the rest of the week executing those decisions - you are not allowed to second-guess yourself because GTD is all about having "integrity in the moment of choice" regarding your decisions.
I use a similar trick to the scheduling - if I'm undecided, I just start and do all the weighing up while I'm getting on with it. Once you've started, chances are you'll continue as you've already done the hard bit. If not, you don't feel like you've cheated, which, for me at least, is for too easy a habit to fall into.
I was in this exact same scenario yesterday: standing outside my building under the awning with my bike watching the rain come down. I tricked myself into doing it since the rain and sort of been off and on, and in the worst case I could just check out the farmer's market near me and then head home. As it turned out, 10 or 15 minutes into my time outside the rain stopped and I ended up riding for more than two hours. I was really glad I sucked it up instead of going back inside, where I might not have gone back out when the weather got better.
Some argue that this applies to other feelings, even to love; that if you act as if you love something, then the feeling of love will follow: love is a verb. Here's a striking clip from Paris Je T'aime that demonstrates it (though not, of course, proves it): http://www.youtube.com/watch?v=gIa0454xfyI