The one thing discussed throughout the film is happiness: What is it? How does one find it? How does one keep it? How does one lose it? Is it something that can be located outside yourself? Or can it only be found inside? Does it change with circumstances? Can it be fostered in others?
Throughout the film, the lives of a number of different characters intersect in often seemingly unimportant ways. All of them are intelligent in their own ways; all of them are going through major emotional changes in their lives; all have their own opinions about happiness, what it means, and how to get it. It's a film about chances taken and missed, about opportunities for both failure and redemption, about the beauty inherent in both.
The acting is simply amazing, headed up by Matthew McConaughey, John Turturro, and Alan Arkin. The directing seems nearly flawless. The camera work is stunning. The entire film was complexly beautiful, moving, and intelligent.
I think, in the end, what I loved most about the movie is that it looks at both the good and the bad in human behavior, experience, and emotion. Without being preachy or blindly optimistic, it gave me hope. It gave me things to think about, without seeming to try to communicate one specific message. I think it's a movie from which a dozen different people might take away a dozen different messages ... and they might all be right.