1. You don’t want to go back to being single. You would rather be in a relationship — any relationship — than be single again. You don’t want to be the only one in your friend group who doesn’t have a partner. And you don’t want to be questioned by every relative about when you’re going to settle down. It’s easier to stay in the relationship you’ve already built than to tell everyone you’re single again.
2. You really want a wedding (or children or a house). You’re not staying with this person because of how excited you are to spend forever alongside them. You’re staying with them because you’re excited about the milestones they’re going to help you reach. You’ll get to walk down the aisle. You’ll get to paint a nursery. You’ll get to own your own home. You desperately want to check certain items off your bucket list and you feel like they’re not going to get accomplished without this person, so you stay.