I've been a fan of all Glenn's articles for a while now, since he always manages to bring in relevant points, and come up with solutions and suggestion in a very clear and concise manner. In this specific case, I've had many swimmers in the past that could benefit from backing off from 'hard work' a little, and putting in more 'smart work'.
Don't get me wrong, every coach likes working with swimmers who are willing put their heart into a set, and ultimately a swimmer needs to put in a lot of hard work in order to achieve personal success. However, many times swimmers (and other athletes) forget that the mind controls the body, not the other way around! Thinking about your swimming, analyzing your own strengths and weaknesses, and coming up with solutions and ideas to improve is just as important as pushing through that third quarter of the set (and race)!
Check out the link for more on how to do this!