laugh and the world laughs with you
Keep your sense of humor and people will sympathize with you, as in She's always cheerful and has dozens of friends; laugh and the world laughs with you. This expression actually is part of an ancient Latin saying that concludes, weep and the world weeps with you. The current version, with the ending weep and you weep alone (meaning "you'll get no sympathy in your sorrow"), first appeared in 1883 in Ella Wilcox's poem "Solitude." O. Henry used a slightly different version: "Laugh, and the world laughs with you; weep, and they give you the laugh" (The Count and the Wedding Guest, 1907).