Write down your thoughts, and get a dry erase board (whiteboard).

I like writing. Not stories or anything that people will ever read, actually, not even I read what I write.
Writing things down, like my thoughts, helps me think better. It helps slow my thoughts down rather than allowing them to race.

This is a technique I use a lot for my work when I have a difficult puzzle to solve, or when I just need to make a thought process clearer and understand things better.
Without writing, my mind will just race through the thoughts, and as much as I try to slow it down, I cannot.
Writing helps me do this, it forces me to slow down because I cannot write as fast as I think, which means that my thought process will be much slower.

This allows me to actually understand each thought that crosses my mind, each solution I think of for solving an issue is actually thought of and contemplated, rather than just moving on to the next thing.

This has helped me countless times in work and in my personal life, and even though I do love writing and it really helps, I do not like the waste of paper. I do not like the environmental impact it has.
Especially since I almost never go back and read what I write down. So the moment it goes on the paper, it's gone, it will end up in the garbage, and that is just a waste.

The reason I don't read it is that I am just doing it for the effect it has on my thinking process, slowing me down and allowing me to better think and process things. Other than that, it doesn't matter to me if the text disappears after I write it.

This is where the dry erase board comes in.
I can't say that I know how ecologically friendly dry erase boards are, because I do not, but I do know that I am not ok with deforestation and the amount of paper that is wasted and as a result, the number of trees that are killed for nothing.
So, instead of writing on paper, I decided to write on a dry erase board.
This has been a game-changer for me as it's also much easier for me to write on a dry erase board, I can also write whatever I want and be sure that no one will ever read it (if that was something that I worried about).

I have a few small boards and a bigger board for the more intense thoughts I need to write down. When I fill up the board, I just erase it and continue on with the thoughts. Very simple.
All the benefits of writing, just without the paper and without the waste.

So my recommendation is to start writing down your thoughts as you are thinking them, you will be surprised how much this can help you think more clearly. And, to use a dry erase board, even a small one will do (but get a small marker!).