Before Jesus began his ministry, he went into the wilderness where he was tempted by the devil. He had been fasting for 40 days, spending time with the Father. Then the devil shows up. But Jesus was ready. He was ready for spiritual battle.
So, in the 40 days of Lent, we are preparing for spiritual battle. We practice self denial, so that we can focus on the Father.
Celebrating Easter is richer when we're ready.