Take a blank white piece of paper
With a marker draw a small back spot in the center (about 0.5-1 cm)
Stick this paper on a wall using some glue (the dot should be level with your eyes while standing)
Now stand about 8- 10 feet away from the wall
Look at the dot
Keep looking at the dot using all your concentration
Don’t look at anything else
Do this practice daily for about 10 min
Do this for about a month or more if you like