I think people are like butterflies. Some more exotic than others. Some dull, some vivid, and some extraordinary. They bless our presence and at times stay for a spell. Sometimes they leave without us noticing, and other times we watch them fly away, unable to capture them and wishing they wouldn't leave our sight, only to notice another butterfly has arrived.
We can't force people to stay in our lives. Some relationships we nuture, others just nuture themselves. See the butterfly for what it is. A life glance, a moment, a reminder of something for us to learn. Being open to the beauty of life's butterflies allows us to continue to grow emotionally and spiritually.