We often have a tendency to not be aware of where we place our attention. It goes to the area with the most stimulus, the one that's drawing our attention most strongly at the time. Sometimes this is a good thing that needs to happen (responding to that fire alarm) sometimes, not so good.
In fact many people do not realise that they can decide, or at least influence, where they place their attention.
Developing an awareness that we can choose to place our attention on given objects is a powerful thing. It allows us to direct our thoughts and perceptions in a way that we choose rather than where stimulus takes us.
It can be easier to focus our attention if we are very interested in the subject, a craft we love, a piece of art work we really admire, a great book, someone we are in love with. Are all relatively easy things to be attentive to.
I always remember focusing on my father slurping his cereal in the morning. I can become obsessed with people's leaking earphones on the train. I can focus on the negative comments or feedback I get rather than the positive.
In this way we can focus on what is in reality often a small amount of information, and by doing so ignore the majority of the available information. In the process often reinforcing less skilful or negative ways of viewing our daily world. This can result in a feeling of the world being more negative than it actually is, a real shame. This can have a result of increasing our level of stress and anxiety.
Until we learn to direct our attention; where it goes, is where it's gone before, in effect old habits.
So how do we start to be aware of and move where we place our attention.
Well I would suggest starting with the body.
An awareness of how our body feels, how our posture is; are we holding tension? Is a practical way of remembering to check in with where our attention is. I have noticed that if I become aware of slumping, I can then see that I have lost mental awareness. If I correct my spine then my awareness increases without having to 'make it'. If I notice that I have a tight jaw, I also notice that I'm often having negative thoughts.
We can play with attention exercises. Say for the day we will; notice every time we see the colour blue, notice every time we have a judgmental thought, notice ever time we are offered service.
If you have a mind that's been allowed to wonder where it wants for years, maybe decades, then it takes time and practice to 'behave' and go where you want it to. However the results of working on this can be interesting, and in some cases life changing.
If you are interested in taking this deeper, I would recommend the courses held by the Todo institute. http://www.todoinstitute.org/
The books of David K Reynolds are also good places to start