In Zechariah 7:5 we read: “Ask all the people of the land and the priests, ‘When you fasted and mourned in the fifth and seventh months for the past seventy years, was it really for me that you fasted?'"
Richard Foster comments: "If our fasting is not unto God, we have failed. Physical benefits, success in prayer, the enduing with power, spiritual insights—these must never replace God as the center of our fasting. John Wesley declares, “First, let it [fasting] be done unto the Lord with our eye singly fixed on Him. Let our intention herein be this, and this alone, to glorify our Father which is in heaven….” That is the only way we will be saved from loving the blessing more than the Blesser." (Foster, Celebration Of Discipline, p. 55)
That last sentence is spiritual wisdom. Love the One who blesses in the first place, and more than whatever blessing we desire or receive. It's not wrong to desire righteous and godly results. But look how Zechariah encourages us to love God above all, even above results.
What Foster says here about biblical fasting is the same kind of thing Scot McKnight says:
"People fasted in the Bible in response to some grievous event in life – like death or the realization of sin or when the nation was threatened, and not essentially for the sake of getting some beneficial result. “Fasting isn’t a manipulative tool that guarantees results.” (McKnight., xix)“Fasting is a response to a sacred moment, not an instrument designed to get desired results. The focus in the Christian tradition is not “if you fast you will get,” but “when this happens, God’s people fast.” Fasting is a response to a very serious situation, not an act that gets us from a good level to a better level.” (Ib., xix-xx)
Focus on responding to the call of God. Then, see what God does.
I like how The Message interprets this verse.
God-of-the-Angel-Armies gave me this Message for them, for all the people and for the priests: "When you held days of fasting every fifth and seventh month all these seventy years, were you doing it for me? And when you held feasts, was that for me? Hardly. You're interested in religion, I'm interested in people."