Be doing your enjoined activity. To be active is far superior to being inactive, idle. Even the preservation of your body will not be possible without action.
Krishna stresses the need for regular activity for all. We have a body, and we feed and nourish it with relish. As a result, it gains health, strength and energy, all of which are meant to be employed every day, hour and minute in useful activity. Except for timely rest and sleep, our life is meant to be active, effectively so.
To feel hunger, appease it properly, build energy, utilize it for proper activities, again feel hunger and provide nourishment, is a cycle, like others Nature has designed.
Krishna therefore exhorts everyone to be active consistently, without fail. He points that activity is far superior to inactivity, idleness, lethargy.
You cannot preserve the body if you stick to inactivity. Look at the animals, birds and the rest. They come home at the end of the day, but next morning go searching food and nourishment. Activity is indispensable to preserve the body and use it effectively.