Sometimes there are situations unrelated to the holidays, but wishing something good and kind will still be appropriate.
For example, in Russia it is customary to say to the person who comes out after the bath: «С легким паром! / Hope, you’ve had a good steaming!»
And before some important business, such as a student before an exam, it is wished «Ни пуха ни пера! / Break a leg!» The answer in Russian to such a wish would be «К чёрту!» Literally, it means go to hell, And the point is this: knock on wood.
Now you will not only be able to say «С днем рождения!» или «С Новым годом!», but also easily congratulate the person in Russian on any meaningful occasion.