Last year he would never have dared to vow that he will try all year to keep the fast days. Fasting always seemed strenuous to him. He thought of fasting as nice but not really applicable to him.
In the year that passed, Samuel had felt the closeness of God. He knew that when he reached out to God his soul would be at peace. Towards the end of the year, he remembered to try to honor some fast days. Each time he tried to fast a little better. He noticed how his prayer improved. He noticed he was calmer. He noticed his felt closer to God because he was respecting His commandments. He knew an Orthodox Christian shouldn’t ignore anything that was part of the tradition of the Church.
So with the new year ringing in, Samuel thought of vowing to fast the very best he could in the coming year. Fasting was in the law of God anyway. It was required of all Orthodox Christians. So if God requires it, why should he disregard it?
He would never have dared last year to try, but this year he needs to do it for himself. For his own salvation!