One frequent question I get here is why some friends seem to feel more important than their friends. In other words, why does a friend feel that their time is more valuable than anyone else's? There are times when you need to adjust. Life changes, after all. But there are also times when you may be stuck in this "well I'm busy so you need to come to me" attitude even after you aren't that busy anymore. Your schedule may change, your friendship will change, but your attitude should always be one of gratitude with friends.
Sometimes a friend will get a new job or have kids, and for a temporary time their schedule will be out of hand. Their friends will understand, for a while. Eventually though, friends need to reciprocate and make time for each other. If they don't, the friendship will wither and people will drift apart. Here's more on what happens when you think your time is more valuable than your friends. Don't allow a change in schedule to end a friendship. It doesn't need to be that way.
Remember, your friends want to support you and be there for you, but if you develop an attitude where you think you are more important (that your schedule or time are more important) you may lose a friendship.