“Barnabas was determined to take along John, who was called Mark. Paul, however, was not in favor of taking him along with them […]. At this there was a sharp burst of anger, so that they separated from each other.”
~Acts 15:37-39

All three men involved in the discord were spiritually strong and had an extraordinary record of service to God. (Acts 13:4,5)
Still, there was at least one occasion in which Paul was disappointed by Mark, and eventually, he and Barnabas had a grave argument about it.
In time, though, Mark took on more responsibilities and even wrote a gospel account of Jesus’ life, having been eyewitness to some events. (Mark 14:51,52; Phm. 23,24; 1 Pet. 5:13)
Some time prior to the completion of the gospel, Paul came to forgive Mark and even requested his company in Rome. (2 Tim. 4:11)
This account teaches us that while Christians should constantly strive to display patience and self-control, we are not perfect and from time to time, will have serious disagreements with other mature Christians. (Gal. 5:22,23)
But much like Paul, Barnabas and Mark, such disagreements should not impede our desire to continue serving Jehovah to the best of our abilities. (Acts 15:39b,40)
That a fellow believer has a differing point of view does not automatically disqualify them as a spiritually strong person.