I guess what I'm trying to say is, we need to make time for friends even when we are in a relationship. They, too, have feelings and it does hurt to be sought out only in times of trouble. You don't need to go out with them often. Just make time to say hi or hello every now and then. It should not be difficult nowadays. There's Facebook, Twitter, Instagram and what-not. Much better if you can have coffee or lunch or dinner with them some time. Doesn't have to be a grand get-together. Just make time. And when they extend an invitation, the least you could do is respond. Whether you are going or not, have the courtesy to respond.
Friends are rare and precious stones but they are not as hard.
They have feelings and you hurt them by ignoring their invitation, or saying no all the time. They can grow tired of reaching out and the next thing you know, you no longer have friends to turn to.
Just sayin', you know ;)