Working wife comes home and feels it is unfair that she still has all the home responsibilities including childcare.
Sex-starved husband feels he earns 90% of income and is a good husband but resents that he gets no sex.
Young woman had fantasy expectations about financial capability of fiancé;
he bought her a smaller than expected engagement ring which she resented for years thereafter.
You and your partner are living together and now it is time to buy a house. They make much more money that you do and want a pre-nuptial to protect themselves in case things don’t work out. You are highly resentful that they don’t have more commitment to making it work.
One partner starts texting an old flame and other finds out about it.
Feels violated and betrayed even though nothing sexual occurred.
One partner actually had an affair but both of you desperately want to save the marriage.
Inability to forgive is a major hurdle.