The GILH turns its attention next to the Daytime Hours, terce, sext, and none:
74. Following a very ancient tradition Christians have made a practice of praying out of private devotion at various times of the day, even in the course of their work, in imitation of the Church in apostolic times. In different ways with the passage of time this tradition has taken the form of a liturgical celebration.
75. Liturgical custom in both East and West has retained midmorning, midday, and midafternoon prayer, mainly because these hours were linked to a commemoration of the events of the Lord’s passion and of the first preaching of the Gospel.
76. Vatican Council II decreed that these lesser hours are to be retained in choir. [See SC 89.]
The liturgical practice of saying these three hours is to be retained, without prejudice to particular law, by those who live the contemplative life. It is recommended also for all, especially those who take part in retreats or pastoral meetings.
77. Outside choir, without prejudice to particular law, it is permitted to choose from the three hours the one most appropriate to the time of day, so that the tradition of prayer in the course of the day’s work may be maintained.
78. Daytime prayer is so arranged as to take into account both those who recite only one hour and those who are obliged, or desire, to say all three hours.
I found this slightly expanded commentary on the daytime hours at the Genesee Abbey web site:
Terce, a Latin term for third hour, is prayed at mid-morning. It is a shorter prayer referred to as one of the little hours. Traditionally it is dedicated to the coming of the Holy Spirit which took place at mid-morning in the account found in the Acts of the Apostles. One prays for light and strength as the day waxes strong and one’s work begins.
Sext, another of the little hours, is Latin for the sixth hour. It takes place at midday when the sun is at its apex and one has become a bit weary and mindfulness is all but impossible. It is a time for earnest prayer to resist temptation, to keep from being overcome by the demands and pressures of life. We are reminded of Christ being crucified at the sixth hour and we unite ourselves with Him. One is aware of one’s failures and mistakes and prays for deep and abiding conversion even to the point of sacrifice.
None, refers to the ninth hour, roughly mid-afternoon, and is the third of the little hours. It is a time to pray for perseverance, to pray for the strength to continue bearing fruit as one reaches one’s prime and needs to keep going. It is a time when one becomes aware of the sun’s gradual descent and the strength one needs to cope with the demands and responsibilities of life.
Catholic Sensibility 
I’ve read that, before the council, Prime was the hour that the Church recommended specifically for the benefit of the laity. Given that the council so strongly encouraged the recitation of the office among the laity, any idea as to why it chose to suppress Prime?
I suppose it was thought that it duplicated some of the themes of Lauds, and that it added little of distinction. If I recall, the difference for Prime from Lauds was that it was themed along the lines of beginning the monastic work day. I suspect the council bishops concluded Prime was a duplication of sorts among the minor hours and that the theme of commencing the work day and praying for strength could be folded into the prayers and rituals of the prayers at dawn.