It was sacrificial. If believers are going to have an attitude like Christ it must be sacrificial. Sacrifice is fundamental to unity. If that obtains then we will not merely concern ourselves with our own interests. Everyone cannot always have their own way.
Someone has to give.
Jesus was willing to spend and be spent for us. He qualifies as the greatest example of lowliness of mind. He followed the path of utter selflessness. Yet he was God almighty, the highest of high. He went to a criminal's death, the lowest of low.