The Pharisee had an attitude of a merit system. A merit system is trying to earn it by works. God has promised to reward the faithful fasters, but this reward is not to be claimed as merit or works least any man should boast (Ephesians 2:8-9). No matter how much or how long we fast we do not earn or deserve to be rewarded for what we do.
But without faith it is impossible to please him: for he that cometh to God must believe that he is and that he is a rewarder of them that diligently seek him. (Hebrews 11:6)
It’s your diligent seeking for the right reason that brings the reward. Notice the Pharisee's result; he prayed with himself. Praying and fasting by works is praying and fasting with yourself, it goes no higher than you.
When we fast, we are merely doing our reasonable service. (Romans 12:1) Fasting is to humble yourself before God, not that you put enough pressure on God by fasting so well that God cannot resist rewarding you. Fasting deals with you, not with the Lord Our God because the Lord God never changes (Malachi 3:6). He is the same yesterday, today and forever. (Hebrews 13:8)
Be like the publican he honored God not by works but by humbling himself. He was honest before God. His end result was he was justified and exalted by God, not by works.
That's why fasting is the greatest secret hidden in plain sight in the bible. Now continue to fast for right reasons.