How do you know when to let go?

Have you ever had a friend or family member that wanted to be around you as long as you were helping them,

but when you needed help, they were suddenly unavailable?  Have you ever felt abandoned by a loved one in your

moment of need?  If so, how did you handle it?  What did you do about it?  How do you know when to hang on to

your relationship with such a person and when to let it go?  Futhermore, if you hang on to it, how do you address

the issue with them, if they don’t want to deal with what you are feeling?