On the wandering nature of the mind

Q: My mind often wanders, thinking about unimportant things. This movement has a strong power of recurrence, in spite of my efforts to check it.

You must go on rejecting it till you get the mastery of it.

The mechanical mind is a part of the constitution of human nature and its activity is a well-known phenomenon, not due to something wrong in the spinal chord. What is unusual in your case, is the absolute helplessness of your will in the face of this very ordinary phenomenon. If that is due to the spinal chord, it is another matter, but the real cause there too is psychological.

– Sri Aurobindo