Block thoughts with affirmations.

“Seek the Self by meditation in this manner:

TRACE EVERY THOUGHT TO ITS ORIGIN WHICH IS ONLY THE MIND.
NEVER ALLOW THOUGHT TO RUN ON.
If you do, it would be unending.
Take it back to its starting place again and again and the mind would die of inaction.

Go back constantly to the question
‘Who am I?’.
TEAR EVERYTHING AWAY UNTIL ONLY THE SOURCE OF ALL IS LEFT.
And then live always in the present, only in it.
There is no past or future except in the mind.”

– Bhagavan Sri Ramana Maharshi.