I previously discussed the myth of multitasking–we can't do it. Our perception merely reflects how adept we are at shifting from one task to another. But no matter how well we do it–there is a period of time in which we are NOT doing either task. It is the nature of this hiatus which can be troubling and even dangerous. We also loose continuity when we try to multitask since we are breaking one flow of thought to introduce another.
Thinking works the same way. We cannot hold two separate thoughts in our mind simultaneously. But that is not necessarily a bad thing.
It offers us a potential for healing. We can actually 'change the subject' in our mind. When we find ourselves obsessing over negative thoughts, scenarios. When we are burdened by worry and concern and yet are unable to change anything, then the truth of one-thought-at-a-time can be healing.
It is the basis of some meditative practices as well. Repeating a mantra and focusing in on it takes our mind away from other more disturbing thoughts. Going back to concentrating on our breath does the same thing. We change our focus.
Practitioners of meditation are adept at training their minds. They can displace negative thoughts with neutral or positive ones. This is not easy for most of us. But at least the awareness that it can be done should be somewhat comforting.
At least we can try it out.