Fasting and seasons of festivals are part of the law of Moses, and that law is good, god inspired, and profitable. So times of discipline and asceticism need to be balanced with times of celebration. Feasting all the time is bad for you, but so is not celebrating.
Christ is the bridegroom for the church, and when he was with us it was a season of celebration. That time ended: the apostles fasted, and Christ said we should fast. Intermittent fasting is fairly good for you, according to modern reviews.
Not all will celebrate in the same seasons. Circumstances will change. So, on these issues, we are instructed. Don't judge. You don't know if you are looking at fabric or a wineskin.
14 Then the disciples of John *came to Him, asking, “Why do we and the Pharisees fast, but Your disciples do not fast?” 15 And Jesus said to them, “The attendants of the bridegroom cannot mourn as long as the bridegroom is with them, can they? But the days will come when the bridegroom is taken away from them, and then they will fast. 16 But no one puts a patch of unshrunk cloth on an old garment; for the patch pulls away from the garment, and a worse tear results. 17 Nor do people put new wine into old wineskins; otherwise the wineskins burst, and the wine pours out and the wineskins are ruined; but they put new wine into fresh wineskins, and both are preserved.”
1. In the old, catholic system, with established churches, one could not marry during a time of fasting: one was baptised generally at the end of Lent. But death would take people, and mourning could occur at any time.