So Abram departed as the Lord had spoken to him, and Lot went with him. And Abram was seventy-five years old when he departed from Haran. Then Abram took Sarai his wife and Lot his brother’s son, and all their possessions that they had gathered, and the people whom they had acquired in Haran (Gen 12,4-5) 

When Abram received the Lord, his life split in two parts - before and after that. He left idols and began to worship a new god, for whom (unlike the surrounding tribes) he had no visible likeness - he was invisible. He was surprised to find that this God was communicating with him, often helping him, but perhaps even more surprising was the discovery that this god cared about how Abram lived and was even interested in his inner setting - for example, whether Abram believed him or not. Compared with the kind of worship he had practiced before and seen around him, this was truly shocking.

On the way from Ur to Haran, their caravan covered about 800 km. Is such a long journey worthwhile? And it's not over, his God sends him further - but does it make sense to move on when we're doing well here? We have acquired property and slaves, will we choose certainty or risk? Can anyone guarantee it will continue to be better elsewhere?

It was not the first time that Abram had to make a decision between the temporary and future good. He had not yet thought of eternity (btw. this word was used for the first time by his new god), but he had to decide: further beyond Haran, civilization was at a lower level, the danger was greater. Here the local conditions were at least somewhat similar to what he knew from his native Ur, but what will he meet far out there, in an unknown country?

It wasn't an easy decision, but he did the right thing and set out. But at the moment he did it only because he believed it would be better for him there than here. He had not received the offspring the new god had promised him yet, and he believed that he would see it there.

Do not let us be mistaken: at the beginning of his journey, Abram follows God for his own good. He does not seek any higher ideas, does not think about, does not know them. He is the same as many who set out on this journey voluntarily. However, it is a credit to him he did not remain so.