I know that immobilized feeling well! I have been tackling a lot of long delayed tasks like this lately. For me, the trick is just to get started by doing something small. I typically wind up getting 10x more done than I expected. And if I don't and I only do that one small thing or spend five minutes on it, I've at least made *some* progress and turned off the guilt and negative self-talk.

Here's a couple of ideas that have helped me:

1. Set a timer for five minutes (or two minutes). During that time, clean your desk. It can be really overwhelming to tackle stuff like this because who wants to spend the next three hours dealing with a mess? If you just spend a couple of minutes, it's not so bad.

2. Make a list of 4-5 tiny steps you can take, things that will take less than a minute. One thing you can pick up and put somewhere else.

There's actually a part of the Feeling Good Handbook that uses procrastination about cleaning a desk as an example (page 187 in my copy)! The author suggests using a cost-benefit analysis. First you make a pro/con sheet of the advantages and disadvantages of delaying the task.

The advantages/disadvantages of not cleaning my desk now:
Pros: I can read a book instead. I hate cleaning.
Cons: I feel bad whenever I look at my desk. I can't find what I need. I need to get it done some day and will keep worrying about it until I do.

Then you make a list of the pros/cons of getting started today:

Pros: It will be done. I will have a clean, usable space. I won't have to worry about it anymore. It will make me happy to look at the cleared space. I have been bothered by this since 2005.
Cons: I would have to spend time doing a task I loathe. I would have to make decisions and that's tiring.

So when I look at this list, I have so many more reasons to get the cleaning done with now. Yes, there are some cons, but they will not change because I delay. They are there whether I do the task now or later.