Even when tired, the family used to end the day with what?

The Robinsons are firm believers in God. And their seemingly miraculous deliverance from a potentially fatal shipwreck merely confirms them in their belief. Whatever happens on the island, however much adversity the Robinsons encounter, William always reminds his sons to say their prayers. The family that prays together, stays together, as they say, and the regular ritual of the evening prayer binds the Robinsons more closely together as a family. This is important, as the Robinsons are all alone on the island and really need to pull together if they're going to survive.
The Robinson family has a lot to be thankful for: they've survived a disastrous shipwreck in one piece; they've landed on a desert island abundant in plant and animal life; they've remained a close-knit, loving family despite all their numerous setbacks. The Robinsons are truly grateful to the Almighty for the many blessings He has so graciously bestowed upon them, and they express their undying gratitude in prayer each night before they go to bed.