Overzealous (adjective)

1. Excessively eager or enthusiastic in one's actions or beliefs.
2. Being too eager or enthusiastic in one's actions or beliefs.

Origin:

Derived from the phrase "over zealous" which means "excessively eager or enthusiastic".

Examples:

1. The new employee was overzealous and made many mistakes.
2. The parent was overzealous in their support of their child's sports team.
3. The salesperson was overzealous and made many false promises.
4. The teacher was overzealous in his teaching methods.
5. The volunteer was overzealous in their work and did not take rest.