Psychiatrists blame anxiety - everyone starts with their own experience, yet there is a point, as in the brain, the hippocampus reacts poorly (to anxiety) and makes it difficult to organize your thoughts (by interfering with short-time memory). You are going to have your own way through this.

Some recommend mediation. That is a fancy way for saying to train yourself to focus.

Do not ignore nutrition. There are so many additives in foods, different people can respond differently to them.