Oprah Winfrey once said, and I would like to quote and edit: 

“If friends people disappoint you over and over, that’s in large part your own fault. Once someone has shown a tendency to be self-centered indifferent, you need to recognize that and take care of yourself; people aren’t going to change simply because you want them to.”

As I grow older, I see people drifting apart, little by little.

Some friends cannot find time to check up on others or reply to emails.
Some family cannot manage to remember important dates.
Some spouses who couldn’t be bothered to buy each other flowers. 

Some promises which have been long forgotten.

As difficult as this self preservation seems to apply in real life, it is the key to peace of mind. I hope you don’t have to – but if you are in such a place, don’t fret, you’re going to be okay.