One thing was obvious about Jesus and the disciples - they enjoyed life and loved people.  But that was a sharp contrast to the religious leaders who enforced many restrictions in the guise of 'pleasing God'.  Their attitude was mournfully dutiful, sending outward signals of holiness, even if they had no relationship with God.  One set of rules was about fasting.  This was intended to be a normal part of submitting to God and praying for His purpose to be revealed and fulfilled.  It was not wrong, but it had a specific purpose in moving people's focus away from themselves onto serving God, while waiting for Him to appear and claim His people.  But the publicly pious Pharisees turned fasting into a self-seeking circus (Luke 18:9-14).

Why did Jesus' disciples not fast?  Because Jesus was God!  He did not encourage them into funeral-like religious practices in the hope that God might come one day ... He had come! (Matthew 11:7-19)  In the same way that a wedding is a celebration of two people who now belong to each other, Jesus wanted the disciples to celebrate His awesome love and power, and their joy that they belonged to Him.  Whatever fasting and praying they did was not for social display or religious approval, but a private matter before God.

Of course, as Jesus said, He would leave them (for His crucifixion and ascension until the second coming) and they would fast in those days (John 16:20).  Nevertheless, they were not left alone, because the Holy Spirit would come to them (John 14:15-21).  So today, those who trust in Jesus should enjoy the living presence of God and hold onto the promise of the physical return of Jesus (Titus 2:13).  

Fasting is never appropriate as a way of winning points for God's favour: but it is useful as an aid to personal prayer. However, as Jesus said in Matthew 6:16-18, "When you fast, do not look sombre as the hypocrites do, for they disfigure their faces to show others they are fasting. Truly I tell you, they have received their reward in full. But when you fast, put oil on your head and wash your face, so that it will not be obvious to others that you are fasting, but only to your Father, who is unseen; and your Father, who sees what is done in secret, will reward you."  So, you do not need to make a show of religious practices at work: but we all need to prepare in private so that we can celebrate our joy of belonging to Jesus in the workplace and community as well as in the church.