Attention to any subject includes it in your vibration (your experienced or psychic reality) and makes you an attractor to more of the same. Meaning if you focus on something that makes you feel bad this will impact on your feeling state and that feeling state will act as a magnet attracting more events that generate a similar feeling response.
Basically, the mind and emotions (your psychic reality) are seen as magnets drawing experiences that produce feelings in alignment with one's current mental state and also influenced by previous focused thoughts.
It is also argued that focusing our thought on a certain outer event or object will help propel that thing into our lives. Here we are looking at the thought part of our nature and it's workings through the LOA. All thoughts will have an emotional or feeling component of course and the interaction of these two to generate an attractive force is something I am still in the process of understanding.
For more information on this topic I recommend the book "The Message of a Master" by John McDonald, available as a free download on the internet.