It happens that I can't really 'start' with work due to having too many things to choose from, or by not knowing how to really get started with it.
What always helps is writing down on a piece of paper a step by step guide of what I will do. this can be very general. But just having the steps written down helps me get started.
Kind of like a "todo list" except that I don't update it when I'm done.
This helps me when I need to make a choice for what to work on, but also to compartementalize the problems that I get stuck on.
For example, on my paper it says this at the moment:
-> Extend importsystem
-> Write parser for text-data
-> check if data in system!
It's just a rough outline for what I should be working on at the moment (instead of being on HN, probably).