A great exercise to train your concentration in your daily life is the “point-focus”.
Paint a dot on a piece of paper and fix the paper on a wall on height of your eyes. Sit down on a chair in an upright position in about 2 meter distance to the wall. Fix the dot with your eyes and stay relaxed during the whole time.
Imagine a light beam which you send to the dot. Each thought or feeling which distracts your concentration from the dot, disperses in the light beam.
Execute this exercise in the beginning only as long as you are able to stay relaxed. With regular practice you should be able to sit and concentrate about 10 minutes.
Repeat this exercise one to a few times per day, until you are able to concentrate, location-independent, on a given point to get rid of needless thoughts and feelings. In this way, you become the master of your thoughts!