I do not deal with that plans cancelling stuff a lot of times. Especially if there is no reason like an emergency or accident but the person just rather wants to spend time with someone else. I also will not argue like crazy if this happens to often, I will just stop making plans with these people or make plans that are not unconvenient to me if they are cancelled (like close where I live, have a Plan B for the day, not much planning needed, etc.). People are growing apart and that is just as it is when you get older.