It is easy to understand the woman whom Jesus said lost a coin (believed to be part of the ten coins indicating her marriage), and she cleaned the house, looking everywhere for that coin. When she found it, she rejoiced, and told her friends and neighbors about it, wanting them to rejoice with her (Luke 15:8, 9).
It is frustrating to lose something, because you know it should be easy to find. When you find it, it is a good feeling just like the woman in the parable.
However, the point of the parable was this,
“Likewise, I say to you, there is joy in the presence of the angels of God over one sinner who repents” (Luke 15:10).
When a sinner repents, do you rejoice as when you have found a lost valuable?