That's why you need a system for recording all the things you can do, what context you should do them in, and keep working on your main task. Once the time is right, you go back to the things you wanted to do.
I can't claim to be an expert at this but I recently watched these vids thesecretweapon.org and coupled with what I already know from GTD and the Pomodoro technique its going well.
True. That's why I've started using a variant of Autofocus[1] (a task system, much simpler than GTD) and am intending to try Pomodoro.
Ultimately when you see the various things you need to do on a list, your intuitive mind automatically prioritises certain things over others. That's how you can reduce yak shaving and bikeshedding; by attacking tasks with shorter 'dependency chains' and higher urgency.
I can't claim to be an expert at this but I recently watched these vids thesecretweapon.org and coupled with what I already know from GTD and the Pomodoro technique its going well.