In short your partner will have a desire to leave if they cannot see a future with you, or the future they can see is one they fear having.
Of course what they are experiencing is a perception of what might be, but to them it feels real and so taking how they feel seriously is important.
When someone in a relationship goes for prolonged periods of not feeling good about themselves in the context of their relationship they have to find ways in which they can feel happy.
What the relationship experiences is where it used to fulfill the needs of the individuals it no longer does and so the individuals start to look outside of the relationship to feel good again.
Woman may go to friends, children or parents to feel important or secure. Men might work longer hours to gain the same security.
The couple can start to resent the areas of their partners life that have taken their place.
If this goes on for too long the next stage is fear for their future as resentment starts to settle in. As life becomes more difficult for the couple and harmony has left the relationship, both people can start to meet their needs in way that contradicts what in normal life they would class as bad behaviour.
They start to behave in ways that are the total opposite of what they really believe in. In these places activities such as affairs become a real possibility.
What’s key to understand is as soon as anyone in a relationship is not having their critical needs met they will have no choice but to go elsewhere to get them met. This is not choice it is a critical human need. You maybe thinking that sex is the driver, but in many cases it’s a need to feel important, loved, secure or maybe just to have adventure where the relationship is stale.
So unless you know what your partner needs how can you help them meet them. If you don’t know what you need how can your help your partner be successful with you.
Many couples fall into this trap, they have no idea how to communicate what they really need and so the relationship is basically a ticking bomb.
It will end up either over, or passionless… Do you understand your partners needs?