Every Successful Relationship Is Successful for the Same Exact Reasons
If there is a bedrock of respect for each individual's interests and values underpinning the relationship, each individual is encouraged to foster their own growth and development. Each individual will evolve in different and unexpected ways.
When you commit to someone, you know who they are today, but you have no idea who this person is going to be in ten years. You have to be prepared for the unexpected.