“We are Jews by birth … Yet we know that a person is put right with God only through faith in Jesus Christ, never by doing what the law requires”. 

Gal 2:15, 16 GNB 

Many people believe in God with the feeling that they have to do enough good, and avoid enough wrong, so that God will pat them on the back and say “That’s it, you’ve done well enough to earn your place in heaven”. 
That was the “salvation by works” system that applied in the religion of Judaism. They believed the law had to be obeyed and, if it was obeyed well enough, the person might be rewarded by God with salvation. Paul had learnt otherwise. He had battled for years to uphold the commandments and all the elaborate outworkings of the laws that had been drawn up, but without ever getting the sense that he was right with God. In fact he was dogged by guilt and a sense of failure all along (Rom 7). He was unable to achieve the “righteousness” he sought. But when he met with Christ – then he accepted Christ’s forgiveness of his sins, his guilt disappeared, and he knew peace with God through Christ. Thinking it all through he came to the realization that only through faith in Christ could a person know that he or she was right with God. This applied to Jewish people as well as Gentiles. Being Jewish by birth could never make you right with God. Knowing Christ, irrespective of your nationality, could and did. 
This was the gospel Paul went round preaching. It is still as true today as it was then. You cannot earn your way by good works or obeying the rules. You can only receive it as a gift from God. 

Lord, help me to trust in you, and you alone, for salvation.