How to succeed in doing difficult things

If you want to do something, anything, but find it difficult to do it,
here is the solution for you:

Start small.

That's it. Don't try to do it all at once.
Take a piece and start somewhere.

Small is beautiful.

If you find the piece is too large, take a piece of that piece.

There is a related principle in computer science called "divide and conquer".

How to manage complex plans for a big goal: The 1% goal

This is about managing complex plans for a big goal.
You want to achieve your goal but then you don't want to be too inflexible with your plans.
So, there is a solution: It is called "The 1% goal."
Set the critical part of your big goal as your main goal, and call this the "1% goal".
Then, make sub-goals and plans accordingly.
The 1% goal is the 1% of all that structure you created. You would be fine
as long as you keep the 1% most important part of your goal unchanged.
As long as that stays the same, change the rest in however way it would work
and you will be on your way to achieve your 1% goal.

So, for example, if you want to write your dissertation by a certain deadline,
that should be your 1% goal. Then you set sub-goals such as
this chapter by this day, and then I will work for 2 hours today
4-6pm and again 8-10pm later on, etc. If you can't make 4-6, no problem.
Move that to tomorrow and you are back on track.

You are allowed to make mistakes with the 99% of your goal structure. If you get some of that 99% on point, that is a bonus.
As long as your 1% goal is there, you can make all the mistakes with the 99% of your sub-goals & plans and still achieve your 1% goal.