have too much of a good thing

have too much of a good thing

To have an excessive, unhelpful, or harmful amount of something that is otherwise enjoyable or beneficial. You're going to hurt yourself if you keep exercising this much. You can have too much of a good thing, you know! The added security features on the new phone are great, but I guess you can have too much of a good thing because they make it incredibly difficult for even the owner to access the device.
See also: good, have, much, of, thing
Farlex Dictionary of Idioms.

have too much of a good thing

Prov. To hurt yourself by overindulging in something good. I've gained five pounds from all the holiday dinners I've eaten this month. I think I had too much of a good thing. Alan: We're having such a good time at this resort, why don't we stay another week? Jane: I think we'd get bored with it if we stayed that long. You can have too much of a good thing, you know.
See also: good, have, much, of, thing
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • too much of a good thing
  • a fat lot of use
  • a good trip
  • good trip
  • put the dampener on (something)
  • put the damper on (something)
  • you're wasting my time
  • put a damper on something
  • dampener
  • damper