Can a believer boast that he was smart enough to get saved?
No. Salvation is not earned by human intelligence, reading ability, or personal wherewithal. Escaping God's punishment comes only through accepting His pardon by grace; God Himself put the finger on the individual. Therefore boasting in one's own smartness is excluded.
Les teaches that this is how God's sovereignty in grace works. We were hell-bound sinners just like everybody else and just as deserving of God's punishment as anyone could be. The reason we escaped is that we accepted God's pardon, and now we are set free, while many family members, loved ones, and friends go on to their just dessert. Les stresses that the only reason we escape is the grace of God. He says we can never boast and say, "Boy, aren't I glad that I was smart enough to read and that I had the wherewithal to..." No, we don't. It is only by the grace of God that God put the finger on you and on me. After we're saved, we can understand that God had us in His sights before the world was ever created.