In time, we lose our freshness and spontaneity of true conversation. These are areas in which everyone interested in self-improvement will seek to improve.
Here are some of Dale Carnegie's courses that can help the following.
Develop increased flexibility through the use of expression, gestures, and voice modulation
Demonstrate ownership of unfamiliar material
Present written material in a captivating manner
Improve your delivery of written material
Overcome barriers that restrict your flexibility