* Fear of exposure: Harry knew that using magic in front of Muggles (non-magical people) was dangerous. He was afraid that the Ministry of Magic would find out and punish him for breaking the Statute of Secrecy.
* Protecting Dudley: Harry understood the potential danger magic could pose to Muggles. He didn't want to hurt Dudley or make him aware of the magical world.
* Keeping his secret: Harry wanted to keep his magical identity hidden from the Dursleys, especially from Dudley. He wanted to avoid the unpleasant consequences of their reactions if they found out.
There are a few occasions where Harry accidentally used magic in front of Dudley, such as:
* The incident with the hamster: In the first book, Harry accidentally conjures a "tail" for Dudley's pet hamster, which he later tries to explain away as a "trick."
* The incident with the fireworks: In the third book, Harry unknowingly causes the fireworks to malfunction during Dudley's birthday party, leading to chaos and a cover-up.
However, these were accidental occurrences, and Harry always went to great lengths to avoid using magic in front of Dudley intentionally. He understood the importance of keeping his magical world separate from Dudley's Muggle life.