Good morals are pleasant to be around, but mere human morality is at best, temperamental and riddled with hypocrisy. As a matter of fact, good morals left to themselves is nothing more than legalism. It was the main portion of the Pharisees' religious diet and Jesus constantly took issue with them.
Christians who boast of their own good personal morals are not participating in God's process of being perfected in love. For that matter, Christians have nothing to boast about except the cross of Christ; yet to even boast in this requires we strive alongside the Holy Spirit, allowing our minds to become renewed. We then progress into ambassadors of God's love, rather than stagnating as meager representatives of human morality.
Now a righteousness that counts comes only by faith in that Jesus shed blood was enough for God to receive us. However, our Godliness is shaped by following the same journey Jesus took to the cross. What does that journey look like? We cease to count our life as our own, but surrender it to the glory of the Father, that He may glorify us just as He glorified His Son.
The reason the road is so narrow is because it was not designed to accommodate any human baggage.
Being a Christian is more than doing good, more than maintaining composure, more than behaving civil. We should never boast about anything we find good within ourselves, as though through our own efforts, we did not receive it from the Author of our life. If there is any good in this world, it is because of God's grace alone.
"No one does good. Not even one." (Romans 3:12)