There are two meanings of the phrase taken for granted. The first, often maligned, is the tendency to take a friend, or a job, or a partner, or a loved one "for granted," meaning to neglect the responsibilities that go with having those relationships, and assuming those relationships will be present and available regardless of how much care is given to them. This sort of taking for granted is often what causes us to treat those to whom we are the closest the least well.
But there's another sense of taken for granted--one that's best expressed in the experience (nearly) all young children have with their mothers: "I can take for granted that mom will be there--if I cry, if I fall down or have a nightmare. She'll be there." Having this level of security is critical for meaningful relationships to thrive. It's what allows couples and friends to raise issues with one another that could lead to a fight but need to be raised anyway. It comes with being able to relax and say, "Things are okay. I'm not going anywhere. I know you're not going anywhere. We can get through this."
This second sense of taken for granted reminds me of my fire-building days as a young Boy Scout. When a fire is just getting started, I learned, it requires a lot of care. You add small pieces of dry kindling, blowing gently, and then progressively larger and larger pieces of wood, tending it along the way, until it really gets going and you're able to add some big logs. Sure, you've got to keep an eye on it, add a new log now and then, but it doesn't need the same tending.
When we over-tend our relationships, they remain insecure, we keep them small, and we keep our lives small. It's important to know when and how to settle in, to let ourselves count on someone, to let down our guard. To give up the need to constantly be tending.