One trick that helps me be productive is to expect that I won't finish an entire task in one sitting. I used to have this problem of procrastinating because I want to finish a task in one go. Now it's easier to break up work into chunks and work on them separately, knowing that eventually they'll all be finished (not working up myself too much in expecting I can finish them all).
I also found this book "Your Brain at Work" really helpful, especially in the chapter about what gets us motivated (a bit of anxiety coupled with novelty helps).