They Support Your Decisions, Even If They Don't Totally Agree With Them
Even if they don't think it's such a great idea for you to drop out of grad school or dye your hair pink, a partner for life will back you on any decision you make, as long as they know that it's really what you want. And they don't blindly support you — they'll make sure that you totally understand the outcome of your decision before you make it, but once you're made up your mind, they've got your back.