on your own ground
on (one's) own ground
1. In the place or area where one is locally established. The team will be playing the championship match on their own ground this weekend, which they're hoping will give them a bit of an advantage. We'll be hosting the state-wide high school science fair on our own ground next month.
2. In a field, profession, or area for which one has a deep affinity or familiarity. After a string of unsuccessful action films, the director is back on her own ground with a biting new historical drama. I tried a few television roles, but I'm really only on my own ground when I'm doing stand-up comedy.