Don't cry because of one person. Remember, there are still 6,790,062,216 people to smile to.
Never let one person bring your whole world down. Yes it is true that at times people who we thought might never let us down, end up doing so, and sometimes those who we thought will love us and be there for us forever suddenly leave our lives. While it is natural to grieve, never waste too much time dwelling on a past or person that you can't change.