Remember back when you were a schoolkid, and you (or your parents) would lay out your clothes for the next day before you went to bed?
I do the same thing with my writing, and it's by far my most useful productivity tool. Each night, before I go to bed, I put together a short checklist of my primary writing tasks for the next day.
This helps me in three ways. First, it helps me avoid undirected activity when I first sit down at my computer. Instead, I sit down, look at my writing checklist, and start in on one of the items.
Second, my brain can't subvert me before I begin. If I start in on a task without thinking so much about it, I can get quite a bit of writing done before my internal critic catches up with me.
Third, my brain subconsciously works on these writing tasks over the course of the night, and it often makes my writing tasks laughably easy to complete.
Setting out my clothes the night before saved me from the existential angst of deciding what to wear each day. Setting out my writing tasks the night before... well, it may not entirely save me from existential angst, but on most days I can get some really good work done before the angst kicks in. Try it.