Joshua 5:12 The manna stopped the day after they ate this food from the land; there was no longer any manna for the Israelites, but that year they ate of the produce of Canaan.
The manna is a reminder of God's presence. He will sustain. He will provide. Israel had enough to eat for all those years in the wilderness. But on this day there was no more manna, because their hope was being realized.
Right now we live in a sin-sick world, but God sustains; He provides. But there is a hope of what is to come, and when the manna stops it will only be because the hope of heaven is being realized.