When a person becomes happy, they get more energetic. This energy is reflected in their body language. The person moves often and changes their posture in excitement.
When a person becomes happy, their backs become straighter, and their posture becomes more upright. Sadness, on the other hand, results in a curved back.
Happiness is strongly connected to confidence. When a person feels happy, they feel better about themselves, and so they are more likely to have any of the common confidence body language postures.
Smiling and laughing
When a person becomes happy, they are more likely to smile often and to laugh at the slightest thing. Happiness increases the tendency to smile and laugh. (See Why we laugh at things that are not funny?)
When a person becomes happy, they will feel more like talking to others. A happy person usually initiates more conversations and talks more.
When a person becomes happy, their ability to focus becomes much higher. When a person becomes sad, they get trapped in their own negative thoughts, and so they may fail to concentrate or follow up with others.
When a person becomes happy, they are more likely to walk faster and with wide steps. Sadness, on the other hand, can make the person drag their feet to walk.
Open body language
When a person feels happy, their body language is probably going to be more open and relaxed. The happy person will hardly cross their legs or fold their arms. (See How to have open body language?)
Smiling with the whole face
When a happy person smiles or laughs, their whole face will reflect the smile, and the smile is also going to last longer than usual.
The body language of happiness
What is Body Language of Happiness And Joy? The body language of happiness