It would be helpful to ask the person who comes into your life, then inexplicably leaves why they do it.. If you have a pattern of dysfunctional and/or failed interpersonal relationships it is a pretty sure sign that you need to change some dysfunction about yourself. A therapist or healthy person who knows you well can help you objectively understand the dynamics of how you interact with others if they are given an accurate detailed picture.

We have heard that God works through people and it is true.
It is through our interactions with people that our shortcomings are brought to light. Conversely it is through our interactions with people that our assets and gifts are brought to light..

We are all teaching each other lessons as orchestrated by Love, The Higher Power, G-d or whatever we want to call it.

It is wise not to assume that we know the lessons others are learning.
We all learn different lessons in our own time when we are ready.

The system that is in place for our evolvement is perfect.
We are all progressing and it won't be long before everybodies life is one big happy...
Smiley Party!