After Abram rescued Lot, the Lord came to abram in a vision and told him not to be afriad, that the Lord was his shield, his exceedingly great reward. Abram then asked God what God was going to bless him with, sense Abram was childless, the heir of his house wasn't his offspring. God brought Abram outside and told him to look towards heaven and count the stars if he could, and thats how many descendants he shall have.
It doesn't say what Abram was afraid of, only that the Lord told him to not be afraid. Regardless of what was keeping him unsettled, God knew it and told him to not be afraid, because God is with him like a shield. We need to always remember that God is with us, he is our shield and we are commanded not to be afraid of anything. Abram had a good relationship with God, not because of his actions, but because of his faith and trust in God. Remember, it doesn't matter if you go to church every Sunday or teach a bible class or help others or read your bible daily, its your faith and trust in God that makes your relationship strong. All those other things are good things to do, but they wont get you into heaven, they wont make you deserve to go to heaven, our actions will never be enough. Thats why we need Jesus, we need a relationship with him, all those other things are great to do, but not enough on their own. Abrams relationship with God was strong because of his faith and trust, not because of his actions.
Abram wanted to know for sure that he was doing what God wanted, so he asked God for assurance when God told him that he would bless him and he would inherit the land and have many descendants. We are fortunate to have the bible to refer to when we are unsure if we are following God's will. So God gave Abram another vision, he showed Abram that his descendants will be strangers to a land that is not theirs and they will serve them, and they will afflict them for four hundred years. God will judge the nation that they serve and after they will come out with great possessions, and as for abram, Abram would go to his fathers in peace, buried at a good old age. In the fourth generation they would return to Abrams land for the iniquity of the Amorites was not yet complete. When the sun went down and it was dark there appeared to be smoke coming out of the oven and a burning torch. The fire and smoke suggests Gods holiness and his righteousness and shows Abram that his covenant was real.