To be clear, it is interdependence, not co-dependence.
Before marriage, your actions and decisions mostly impacted just yourself. Your own bank account, your own reputation, your own credit score, your own time, your own living style.
As soon as you got married, that all changed. You are part of a WE or an US. What you do can have direct impact on your spouse. If you allow your best friend to have the car overnight that means that you won’t have the car for the evening. And neither will your spouse.
You are no longer independent. You must now take your spouse into account. Even if you really just want to help out your friend, and even if you feel queasy saying “I need to ask my spouse about the car” you still need to consider your spouse.
Even if you don’t want others to think you lost yourself to the marriage. You still have to consider your spouse.
It’s your ego vs your spouse/ marriage. You know which it should be.