I am having difficulty finding English idiom(s) for these situations:
A person who was previously poor then becomes arrogant because she/he is rich now.
A person who has been helped (because she/he really needs it) but she/he just walks away (and forgetting the person who has helped her/him) after achieving a comfortable state.
Does this ring a bell: "A rolling stone gathers no moss"?
My native proverb is: "The nut that forgets its skin"