Clarence's mission on Earth, (which will lead him to get his wings if he succeeds) is to turn George's life around, leaving him once more in good cheer. Clarence does this by leading George through a retrospective journey that outlines the impact his life will have if he doesn't kill himself: saving the life of his brother, Harry (who later becomes a war hero and saves others' lives); stopping his boss, the druggist, from dispensing the wrong medicine and poisoning a child; marrying Mary, who would have otherwise become an "old maid"; saving the Bailey Building & Loan Association with his honeymoon money during a run on the bank (thereby saving the homes of many of the townspeople); starting an affordable housing community called Bailey Park; and fathering two children.
George was contemplating suicide because a misplaced bank deposit was threatening to result in the closure of the Bailey Building & Loan. He had tried to borrow from Henry F. Potter -- the cantankerous, Scrooge-like character in the story -- but was turned down.
Clarence's journey through George's life shifts George's focus away from his financial problems and onto the positive effect he has had on others. George realizes that he does want to live and that he has a wonderful life, no matter the money difficulties. Racing home to his family, he finds friends there who have gathered the funds needed to save the bank.
In the end, all turns out well. As George's family and friends gather around him, a bell on the Christmas tree rings, signaling that Clarence has earned his wings.
All three movies speak to us about the possible miracles of Christmas: the miracles that occur when we put others' needs before our own, the miracles that come from the connections we make and the joy we find within our own communities; the miracles that may come true if we simply leave ourselves open to the possibility that miracles exist.
So, dear readers, I wish you a merry Christmas; may the miracles you're looking for come true.