He eats his own dog food.

He has eaten his own dog food for years.

He brings his own hide to market.

He brought his own hide to market.

He is bringing his own hide to market.

He has been his own worst enemy for years.

She is being her own worst enemy by constantly doubting herself.

He paid back in his own coin for all the insults he had received.

He paid back in his own coin by playing a prank on his friend.

He pays back in his own coin.