One straight forward way is to constantly focus on improving your stroke – not in any anxious or stressed way (such as berating yourself for constantly crossing over or lifting your head too high, etc) but with a focus that is much more relaxed. You are aware of your technique faults - probably from a coach or another observer telling you what is wrong - and you focus on eliminating them ... gently. This should happen every time you enter the water. It doesn’t detract from the beautiful sensual feeling you get from your body being supported by, and moving through, the water; it uses that feeling to relax and to focus on specific aspects of improving your stroke.
Another way is to focus on counting your laps or, especially, counting your strokes per lap (see the above article on stroke counting). This is relatively easy to do in a pool (as opposed to the open water) and it is a good test on how well you are concentrating – how often do you lose count of the strokes per lap, or even how many laps you have done? We have all been there and it’s all to do with a lapse in concentration or focus. A similar brain training exercise can be gained from concentrating on a particular complicated training task that your coach has asked you to do. Try remembering the task without having to check the whiteboard every lap.
There are many more concentration exercises that you can do when you are not training hard – one of these is to count your strokes and/or your laps in another language. Don’t know any? Try learning to count from one to ten in a language you are not yet familiar with – not too much of a task. Better than doing crosswords to get the grey matter working.