Detachment helps to improve our quality of life. In our onward moving life, we cannot reap the maximum benefit of any activity, thing or task at hand in a moment, unless we detach from the previous activities, things or tasks first.
In this continuous changing world neither you nor the object around you are going to remain forever. Right from birth until death, as we grow older our appearance, our body, our priorities and our goal change. And also as time progresses in the object around us changes.
As soon as we learnt that it is a nature of an object to come and go, we detach from them. We become wiser, see them objectively and do not get unduly attached with them. By separating yourself from the object, you are able to move on without any repent.
Hence, while performing your duty, learn the necessary lessons and move on with your life without an eye on their fruits.