In this story Abram had just returned from Egypt where he had failed shamefully because he imagined that others might want to kill him. Yet, under the Lord's sovereignty, he had not only been protected, he came back with more riches. He must have been deeply impressed with how futile his own efforts were for protecting himself. He also learned anew how trustworthy the Lord is.
Thus, when they needed to separate, Abram was able to give Lot the first choice. He did not try to get the best portion of the land for himself. He left his portion to the Lord's sovereignty. It turned out that he did not get the most attractive portion of the land. What he got instead was the Lord's appearing and promising him all the land he could see as an inheritance. So the result of Abram's victory over his own self seeking was that he gained more of the Lord along with a promise of inheriting all the land.
On the other hand, Lot's choice of what he thought was the best for himself did not turn out to be a good one. Instead of a closer relationship with the Lord he brought his family into a very sinful environment. Instead of increasing wealth he was taken captive to become a slave in a foreign land. He had already lost everything until his uncle Abram intervened.
Abram was different. He was willing to risk everything in order to rescue his nephew even though Lot was no longer in a good condition. He defeated the enemy armies with just his servants and a few friends. Thus he not only rescued Lot, he won a notable victory.
Victory brought a new reward and another test. Melchizedek, king of Salem and priest of God Most High, came to meet Abram. He brought bread and wine for Abram's refreshing. He brought God's blessing and Abram responded by giving him a tenth of all the spoils, the goods the enemy armies had taken. The test came from the king of Sodom. He told Abram that he could keep all the spoils. The king of Sodom only wanted the people for himself. Abram responded that he would not take even one shoe lace so that the king of Sodom could never claim to have made him rich. Thus Abram kept himself completely untainted by the sinful elements of Sodom. This was another victory.