I get this problem too. I'm incredibly productive when I only have a couple of tasks. But, when there's a lot on my mind, I basically shut down.
Similar to what the other user mentioned, I get moving again by focusing on the easy tasks to feel productive again. I make a simple text file with everything I need to do, sorted by month, and each month sorted with the easiest to hardest tasks.
I write every single thing on my mind. For example, I need to order something online, so that gets added to the list. I have a wedding to attend this month and need a new white shirt, that gets added to the list. I need to wish someone happy birthday next week, so I'll add that to the list. Do I need to book a haircut appointment? On the list it goes. Everything goes on the list. It really helps to clear my mind when I don't have to remember these things.
Then, when I start my day, it's not an overwhelming number of thoughts. I look at the list for this month, and I just choose a task I'm in the mood to finish. Do I want to check off a few easy ones? Do I have the entire day to myself and I can focus on a more complex one? If I'm going to the city, then I can take care of all the ones located downtown.
In short, write everything down, start checking things off the list.
I think writing everything down is very valuable. I also think it is important to drop things that turned out to not be so important. This helps to avoid an ever growing list.
I do this by keeping my list on a small paper (A6) in my notebook. When the page is full, I transfer over only the incomplete tasks that are still relevant over to a new page. Often also refining their scope. This chance of default from 'keep' to 'not keep' has had large impact on how many (useless) tasks I drop, and the associated mental burden.
I find that writing things down "takes it out of my head", which I think is exactly what you're saying.
There's a mental pressure that results from having a number of things on the go at once, and writing each thing down relieves that pressure, probably in a similar way to the aforementioned ticking off of simple tasks.
Similar to what the other user mentioned, I get moving again by focusing on the easy tasks to feel productive again. I make a simple text file with everything I need to do, sorted by month, and each month sorted with the easiest to hardest tasks.
I write every single thing on my mind. For example, I need to order something online, so that gets added to the list. I have a wedding to attend this month and need a new white shirt, that gets added to the list. I need to wish someone happy birthday next week, so I'll add that to the list. Do I need to book a haircut appointment? On the list it goes. Everything goes on the list. It really helps to clear my mind when I don't have to remember these things.
Then, when I start my day, it's not an overwhelming number of thoughts. I look at the list for this month, and I just choose a task I'm in the mood to finish. Do I want to check off a few easy ones? Do I have the entire day to myself and I can focus on a more complex one? If I'm going to the city, then I can take care of all the ones located downtown.
In short, write everything down, start checking things off the list.