If a person wants to be a part of your life, they will make an obvious effort to do so.  Think twice before reserving a space in your heart for people who do not make an effort to stay.

I have found that people who want to be a part of your life will make an effort to be in it.  Surround yourself with people who have same interests in life and goals.  Doing so will allow you to better yourself as well as improve their life as well.