Well, here's what I did:
The care is sort of and almost the same as a Mametchi or a Mimitchi. Back in genoration 2, I got a Memetchi and what I did was never let the hearts drop below 1, never let happy hearst drop below 2, and give average dicipline, but it has to be full before it's an adult.
I don't know if that will work for you, but you can try it out and see if it will!
Hope my idea works for you!
*~Tamagotchi~*