What the Bible says about Fasting as Spiritual Struggle
(From Forerunner Commentary)
God knew that man's continuous struggle against corruption would mature and perfect the character needed to be in God's Family. Because we possess the capacity to sin, when it is coupled with the determination to resist temptation to sin, the resultant effort becomes a spiritual exercise. Like a man training with dumbbells, the repeated resistance builds strength over time.
Dr. Viktor Frankl, psychologist and survivor of Auschwitz, cautions that it is a dangerous misconception to believe that man needs a continuous equilibrium or a tensionless state. He insists, "What man actually needs is not a tensionless state, but rather the striving and struggling for some goal worthy of him." The stress of attaining to a high standard or achieving a seemingly impossible quest betters a person. The bland, satisfied life means little, accomplishes little, and is remembered little.
David F. Maas
Fasting: Building Spiritual Muscle