A sannyasi is a monk: one who does not participate in family life and has withdrawn from society. In a sense, he has withdrawn from life. Krishna does not recommend this kind of renunciation. In fact, he says it is impossible for anyone to “give up” in this way, for as long as we have a body, we have to do a certain amount of work just to maintain it. Krishna does not advise dropping out of life, and the Gita is primarily aimed at people who live “in the world” yet desire genuine spiritual fulfillment.