I’ve talked of my love of Joseph Campbell before, and I would be remiss if I didn’t at least quote him at this apposite juncture:
No tribal rite has yet been recorded which attempts to keep winter from descending; on the contrary: the rites all prepare the community to endure, together with the rest of nature, the season of the terrible cold.
– Joseph Campbell
Whether you’re inventing a ritual in the “real” world or in a world of your own invention, I think studying some examples from unfamiliar cultures is an excellent starting-point. Although our largely-secular societies hardly provide us with a deep understanding of the need for rites of passage, they can serve as obvious turning points for character or plot development.
If you aren’t worldbuilding at the moment, why not create a personal ritual or rite of passage?