Expecting to live happier—if not happily—ever after may explain why some people stay in miserable marriages.  Why do some people continue in unhappy unions, while others cut their losses and leave? Partners often look to the future instead of their current state of happiness when they decide to go or stay. Expecting the marriage to improve is a strong motivation to stick around.

First-time parents who are living with sleepless nights and stressful days can see beyond the present to a future that doesn’t revolve around 3 a.m. feedings. Financially struggling college students arguing over money can look forward to their first full-time jobs to bring home real-world paychecks.

Without the hope of better days ahead, chances grow that one dissatisfied partner in a marriage will look around for an alternative. Will he ever stop drinking? Will she always nag about every little thing? The shaky marriage will survive only until the unhappy partner finds a better option. Is there a better fish in the sea? The alterative doesn’t have to be a romantic soulmate. Living alone can seem more appealing than living in a loveless marriage hell.

Some couples look long and hard for alternatives to their unhappy marriages and can’t find them. But they may still decide to stick around even though they do not expect improvement in their marriage. They may find little satisfaction in their relationship, but they look for ways to get past the squabbling and fighting. The lucky ones end up as roommates rather than romantic partners and find happiness in outside platonic friendships or other aspects of life.

It’s not just a lack of appealing alternatives that bind some unhappily married couples together. We’ve come to think of marriage in terms of romance, but the reality is that the arrangement is grounded in the economics of raising a family. That’s why we see so many unhappy couples who stay together for the sake of the children. They move into separate bedrooms and set up separate bank accounts because they want to avoid dividing children in a bitter custody fight.

Religious beliefs hold other unhappy couples together. Some partners fear their church community will frown on divorce, and guilt proves to be a strong martial glue.

Concluding that marriage won’t improve and prospects for the future are better outside a miserable union drives the unhappy apart. The partner who makes that decision is likely to leave and start over looking for another way to be married happily ever after.

Read more: Why Do Unhappy Couples Stay Together?