These 2 guys disagreed about who they would take along on their missionary journey. Their disagreement escalated to the point where they decided to go their own way.
This appeared to be a terrible situation...
But God actually used this to multiply the efforts of Paul and Barnabas sharing the message of Jesus with the world. He took a seemingly bad situation and brought about incredible results.
I follow a God who is able to take "negative" and make it "positive" in the overall picture of what He's doing in, for and through me.