Try to protect yourself from external stimuli. A lot depends on your perception. If you belong to the auditory type, purchase ear plugs in the ears. If you are inclined to focus on their feelings, avoid to be in the same room with unpleasant people when you need to focus.
Sometimes it's hard to ignore because you do not take the argument without examples, or you are bombarded by a lot of unpleasant news. Then the mind is so tired that clings to any external stimulus, just not to concentrate on the difficult to understand information. In this case, imagine that this happens not with you. There are some things I need to know, reply and forget. Just like combination of words. Only this approach will allow you somehow to abstract from reality and focus on hard data.
To learn how to ignore, say what you want to concentrate. Draw the maximum generalized schemes. Try to associate what you need to focus, with the already known data. Also, you must know why you are doing the required work. A clear understanding of the goals allows to cope with complex tasks. Imagine you have to explain the topic to a child, it will force you to simplify and get to the most important, distract from irrelevant and to see the point.
Helps to abstract the correct positive attitude. Look for the positive in everything that is usually perceived negatively. Take any situation as the only possible. To get rid of unwanted emotions and focus on any problem will help the sport. Sign up in the Boxing section, or hit a pillow every time when negative thoughts interfere with focus on the main issues.