Thank you for the extensive explanation. The problem I mentioned starts rather earlier: say I have X big tasks. I need to split them (applying your described process or otherwise) into smaller tasks. BUT now I'm looking at X x2 tasks: the original X ones, each one getting another task of splitting it into smaller ones. The whole stack becomes only more overwhelming like this...
A big part of the idea with my system is that you only identify 5 tasks at a time. Anything more then that and it becomes overwhelming. So the idea is to peel off the first 5 actionable tasks from your project(s), deal with those before thinking further about the project.
Yes this implies having a general sense of how to accomplish the project and the tasks involved, but no it does not mean you need to have a master plan with every step mapped out. Every 5 steps you get to re-assess and course correct.