Use the adjective zealous as a way to describe eagerness or enthusiastic activity. If you are too zealous in your efforts to decorate the house with Christmas lights, you might cause a power outage for the whole neighborhood.
Zealous is the adjective for the noun zeal, "eager partisanship"; the latter has a long e, but zealous has a short one: ZEL-uhs. It can have a slightly negative connotation, and people are sometimes described as overzealous, meaning they try too hard. Zealous rhymes with jealous (and in fact they both derive from the same Greek word), but don't confuse them: a jealous person might be resentful of someone who makes zealous efforts to achieve success.