Estrangement from important others is a sad fact of life for many people. One of the most painful experiences a parent can have is to be rejected by an adult child who appears to want nothing to do with them. Estrangement between siblings, in-laws, neighbors, even coworkers, is also common.
The reasons for estrangement are as diverse as the parties involved. Sometimes there was a very close relationship in the past, and something happened that created distance.
This may have happened either slowly over time or rather suddenly, but once that distance was created, it solidified into estrangement. Or, the relationship was never as close as it could have been, and the gap just kept getting wider, until there was no relationship at all.
If you're estranged from an adult child, a sibling or someone in your social circle, and the estrangement is their choice rather than yours, you're probably feeling rejected.
Rejection is a powerful emotion that can lead to all sorts of defensive behavior, which in turn can further alienate the rejecting person. If someone has chosen to have little or no contact with you, it's important to acknowledge any softer feelings you may have about that.