You might take a shelf in an alcove, or the surface of the dining table or coffee table, or you could choose the bit that is usually the messiest!
Clear it completely and clean it. Then put back only a select few things. Objects which please your eye, or conjure up happy memories, or otherwise give you pleasure. Something alive - flowers, a sprig of ivy, or a healthy plant. A photograph or a card, just one (you can always swap it for another favourite next week/month). Perhaps a candle. Arrange them carefully. Try a few arrangements - it only takes a thoughtful minute - and ask yourself which looks best. If it doesn't look right, take something away.
Be minimal, if only in this one space.
Every time your eye goes to this space, you will feel a little calmer and more peaceful.
If this works for you, you may like to create a little oasis of calm in each room, or you could extend this practice over the whole room, or the whole house.
Try it with just one small space and see if it works....