The first few days of ascetic struggle during a fasting season are always difficult; not so much because of the fasting per se, but because of what the struggle reveals about the human heart.
Fr. Artemy speaks of this well. "Perhaps the only way for a modern man, crazed by inner pride, to come to humility is to be crushed by life, to be cut into pieces by his sins, and to understand that he hasn't any strength to live without God. Our ancestors were like birds who soared to our Lord; now we must crawl to Him." Props to Bill
Of course, our ancestors in the faith also had to crawl. Their struggle, while unique to their circumstances and lives, was the same podvig. But, oh, how difficult this struggle seems to us in our day with the myriad of temptations undreamt of in ages past and the seemingly irresistible power of the Evil One's juggernaut.