The theological answer, as I learned it, is most clearly spelled out in James 2:14-26, often referenced through the phrase "faith without works is dead". The short version is: faith in Jesus will save you, not good deeds. However, if you have faith in Jesus, then that faith will manifest itself through good deeds. If someone proclaims their faith but doesn't act lovingly, then they don't actually have faith and won't be saved. So a Christian should be a good person not because being good will save them, but because being good is a result of genuine faith.