In my native language (Latvian) there is a word that denotes a superstition, but in a more positive way, somehow. It’s hard to explain, so let me give some examples:
If you swing on the swings a lot during Easter, you won’t get bitten by mosquitoes later in the summer.
If you eat eggs without salt on Easter, you will be a liar;
On Christmas eve you have to run around the house three times, barefooted. Then your teeth won’t hurt.
And so on and so forth.
You can’t really call them superstitions because nobody believes in them anyway. It’s more like fun sayings. Although swings are really popular on Easter here — mostly because people simply like swings. In this case the above quote can be semi-humorously used to justify swinging. :)
The majority of such superstitions have to do with celebrations, but there are quite a few that apply to generic situations, too, like “Broken dishes bring luck”.
The point is that when one starts believing in it and religiously practicing it, it turns into a superstition. But when it’s just a fun quote for the appropriate situation, what is it called then?
Is there a word or phrase like that in English, too?