The garden, which is spoken about at the end of the book, is actually logical thought; which means that to "cultivate the garden" would be to enhance the mind. He never actually lives out his own life, because he is constantly consulting Pangloss. What would Pangloss do if he were in this situation? He ultimately realizes that his previous aspirations of discovering and accomplishing an ideal state of happiness were fulfilled, though his accomplishments were not as grand as he had thought they would be. Instead, he has found contentment in a simpler way of life, his farm. He also learns that everything in life is not evil, which is what he perceived it to be while experiencing his hardships. He ends with saying that Dr. Pangloss was right all along, "everything is for the best."
During the entire book, we see Candide searching for his happiness, his dream being kept alive by attaining the happiness.
He believes that if he finds his mentor, Dr. Pangloss and also Cunegonde, his one true sweetheart, and all will be fine. When Candide is joins up with the both of them, he comprehends that he was right in not losing hope.
Personally, I feel it is best to "cultivate the garden", or enriching your mind, whenever possible. To enrich the mind, is to enrich the spirit. You must cultivate your own garden, because no one is going to do it for you. It is your responsibility, to society and to yourself. In order for the world to nurture, it must change. In order for people to develop, people must change. They must change the way they think, act, and what they believe. They must become free-thinking.