Whether it's a cluttered desk or a cluttered mind, both stands in the way of your progress.
A cluttered mind will cloud your judgement and keep you from making rational choices while a cluttered desk or a cluttered room will make you feel low and procrastinate.
Surprisingly, it isn't too hard to keep your mind and your surroundings clean. Just start small and keep progressing.
Start with your desk. Clean it up. Throw away all the items that you don't need.
Your desk should contain only the tools that you need to do your job. Any additional stuff such as that pile of magazines that you ain't gonna read needs to go away.
Regarding your mind, try not to engage with negative thoughts. Just acknowledge them and watch them pass. Don't dig up the past, connect the dots and go deep with negative thoughts. It's counterproductive.
If you feel like you have too many things to do in a day, just take up tasks one by one and finish them instead of jumping on all tasks at once.
Decluttering yourself and your surroundings is an important factor to productive work. Start looking at it with more importance.
Start small but start right now. Go clean your shit up.