One of the great habits I learned from studying Getting Things Done (GTD) was the idea of taking notes. I'm not talking about note taking in schools and meetings, but just getting things out of your head.
I thought it would be more helpful to show an example. On Saturday mornings, I try to get a bunch of reading done that I put off during the week. I inevitably get ideas and thoughts. However, if I stopped each time I got one, I'd never get through even a fraction of my reading.
What I do is I write down a quick note. Here is an example:
I write down the note and then keep reading. This gets it out of my head - which means I won't lose the thought, but I can keep going. I then go back either later that day or another day and review the idea. I can think about it deeper or maybe take action on it.
Because I do a lot of my reading on my iPad, I use an app called Notes on my iPad that lets me write using my Apple pencil. If I am reading something not on my iPad, I use a notebook and pen.
When you get thoughts, don't let it distract you. Get it out of your head and keep going. This lets you be more productive and efficient.