I've really enjoyed this book by Emily Balcetis. One part that I found particularly interesting is about public speaking. Many people are nervous talking in front of a group, and researchers have found that the way the speaker scans a crowd can be partly responsible for this. When the speaker looks at the group they may think the group is not enjoying their talk, thus adding to their nervousness. As part of our biological wiring as humans to keep us safe, as we scan faces our eyes naturally land on frowning faces faster than happy ones.
Therefore, make it a point of looking for pleasant faces to focus on when speaking in a group, and your nerves will evaporate. Interestingly this technique is taught to people doing Ted talks, as well as to kids who experience social anxiety. When they learn to look for smiles rather than frowns, they reap the benefits well into their adult years!