How we change what others think, feel, believe and do
Our commitment to a relationship depends on how satisfied we are about:
Investments can be financial (like a house), temporal (such as time spend together) or emotional (such as in the welfare of the children). Investments can thus has a ‘sunk cost’ effect, where a person stays in a relationship simply because they have already invested significantly in it.
Rusbult tracked relationships of college students. Their satisfaction and investment were key predictors staying in the relationship, with availability of alternatives as a trigger for getting out.
Cults often have a sequence of 'inner circles', each of which requires increasing investment. To get through these doors cult members have to donate their worldly wealth, go through bizarre rituals, learn lengthy texts, and so on.
To keep a person in a relationship, get them to invest heavily in it.
If you are unhappy with a relationship, remember that the past is past. Look to the future and what you can get there rather than what you have spent and can never retrieve. All you have is the rest of your life.