Keep the Sundays properly during Lent: (and always!)
With temperance and self restraint!
'Anyone who believes that the sacrifices, feasts, Sabbaths, and celebrations of the new moon specified in the Law have been instituted by God for the sake of physical license and relaxation will fall completely into the power of the passions, and will be ignominiously polluted by the shameful thoughts they stimulate. He will be in the sway of the corruptible world and preoccupied with thoughts of bodily indulgence. Dominated by the matter and form of passion, he will be unable to value anything except what is subject to decay, senses, and which in the shape of mental images provides the passion with suitable matter to work on. . . When the soul's contemplative faculty embraces self-indulgence as a divine command, it makes an unnatural use of the senses, not allowing them to express themselves at all in accordance with nature.'
St. Maximos the Confessor
'Brethren and fathers, most people call the present days feasts, because of they get drunk and debauched during them, not understanding that these days demand abstinence from meat, not indulgence in drunkenness and intoxication. That is proper to a pagan feast; it is the business of Christians to exercise self-control and not to satisfy the desires of the flesh, as the Apostle teaches. Nevertheless evil has progressed into law and leads the world as it wishes. But let us, brethren, flee intemperance even in partaking of things that are permitted, for we know that intemperance is the mother of sin.'
St. Theodore the Studite