In the classic Christmas movie, It's a Wonderful Life, George Bailey, desperate and depressed, is ready to take his own life because he thinks his life has been a waste. But an angel intervenes and shows him the radical difference he's made in the lives of so many people and his hometown as a whole. He just wasn't aware of the difference he had made.
I want to suggest that we believers are similarly unaware. At times the devil whispers in our ears that we're not accomplishing anything, that all are efforts in ministry and in following Christ are futile and ineffective. He's dead wrong, and he knows it.
Where am I going with this? A couple things:
1) If you look back at last year and wonder, "What good did I do? Did I really make a difference?", let me tell you that if you were living out your calling to the best of your ability last year, then YES, you did make a difference. You just can't see it.
2) Our job is not to worry so much about the results of our lives. Our job is to be more concerned that we are living our lives in obedience to God and in faithfulness to the settings in which he's placed us. If you are obedient and faithful, rest assured God will use you, whether you see results or not.
So this year, resolve to be faithful in your calling, whatever that is--in family and work and church and community. Resolve to draw close to Christ daily, and he will shine that much more brightly through you. Know that if you are faithful to Christ, you ARE salt and light; you just can't see all the ways in which you are making a difference.