Yeah, like Katherine said, I think your priest was probably encouraging you to say the Jesus Prayer to help you avoid sin. Many persons, myself included, find the Jesus Prayer to be particularly effective in helping to extinguish the passions and get you through difficult moments.
Ultimately, I think you want to get to a place where you aren't saying the Jesus Prayer because of any reward but simply because you want to--because it is one of the best ways to worship and relate to Christ. So saying the Jesus Prayer isn't going to help you get an ice cream sundae delivered from heaven, but we have writing upon writing from great monks to indicate that it is a very effective way to help humans get nearer to God's divine energies.
You need to take serious sins to confession so that your confessor can discuss how you might avoid them in the future and help you repent. Unlike in Protestant denominations, an effective confession cannot be private.