Just think for a moment of how much "stuff" we carry around as clutter in our minds . . . all the jobs we are doing; are yet to complete; yet to even start . . . all our personal worries and concerns . . . all of our worries and concerns about friends/family/colleagues etc etc etc . . . wow, the lists can be never ending!
And then . . . if you read the newspapers and listen to the radio, then there's even more chance of other stuff going in too! No wonder some people find it hard to switch off and get to sleep at the end of their day!!!
So, what to do ?
Maybe just doing a very simple task of writing the "stuff" down on a piece of paper (or pieces, depending on how much there is!) . . . and then analysing it's degree of importance to you and re-writing 2 lists ~ one as an action plan of what, when & how you are going to do each of those things ~ and tick them off as they come to a conclusion for you. The other list is for all the things which are out of your control and you have no effect on ~ which means it's someone elses "stuff" and you can let it move on from cluttering your mind.
Even if you just move a couple of things on each week, then that means you can sleep better at night and focus your mind on the things that you can effect in your life.
Let me know how it goes!
Good luck de-cluttering