The Zohar below tells us that if a person describes another person in a bad way - it will manifest itself. For example, if you call your husband, child or friend "lazy" or "stupid" even in jest, they will become that.
A classic example known to Mekubalim - The GABAI in the synagogue gave blessings to the SICK and many times the GABAI starts the blessing with: "...will heal the SICK" - very bad thing to do! The Zohar below says that SATAN takes the SICK and makes sure all those people become indeed SICK.
How should he say it? "He who blessed our forefathers will heal so and so (omitting SICK)"