Most writers have this problem. Shrinks in hollywood make a lot of money
looking after writers with writer's block.
I feel any writing project has two phases: 1. fear and 2. greed. To get
started in writing, you are stepping into the unknown and you are not sure
if what you write is going to be good or not. So, you are fearful, and you
are paralyzed by the fear. Usually the best thing to do is "just do it". Don
't be a perfectionist. Write whatever comes to your mind. "There is no good
writing, only good rewriting". Once you get started, the momentum may carry
you over to phase two. You feel good about your paper and can't wait to
finish. Along the way, it might be a good idea to get your students, postdoc
, and colleagues to help you such as writing certain parts of the MS, so
that it is not too solitary an endeavor. Having an incremental goal and
reward mechanism also helps. For example, if I write one page today, I will
do something I really want to do. Or when I finish this paper, I will go to
Bermuda for a nice vacation.