Research shows that lasting relationships come down to continued kindness and generosity. The Atlantic did a neat piece awhile ago on what makes a relationship last. It all sounds really simple. Be kind and generous to those you want to stay in a long-term relationship with. Continually show genuine interest in their joys.
As with anything, this article also states that kindness is not something you are either born with or you aren't. We all have the same capacity to be kind to others. Like any muscle, if we've been using it more often it will be stronger for some of us than others. We all have potential to be kind and generous humans. Sometimes we just need to be courageous enough to step into it. For most people, knowing that you have a higher chance of sustaining the relationships you care about will be reason enough to give it a try.
Being a Force for Good 