Supongamos un diálogo así:
A: Lo siento. Cometo muchos errores cuando aprendo castellano.
B: Shit happens.
¿Cómo se dice "Shit happens" en castellano?
In Uruguay and Argentina and also Spain the more accurate translation of shit happens would be the expression: "son cosas que pasan" and most of the time the "son" word is omitted and you just say: "cosas que pasan" (although in Spain it's more common not to omit it).
Another similar expression to express this but that isn't as accurate (can have a slightly different meaning depending the context), is: "son cosas de la vida" (again, you can omit the "son").
In my country Cuba we said Eso pasa o esas cosas pasan... gajes del oficio.
A tu pregunta:
Eso pasa gajes del oficio? Puede decirse " Ese pasa" o " pasa" ?
Debes usar eso:
Gajes del oficio is optional, is a way to said in my country but it's an addon to the phrase.
In Colombia it's not common to translate the "Shit happens" expression literally.
As complement to datelligence's answer you may notice that Shit isn't used in the translated expression.
Some adequate translations can be:
Esas cosas pasan. / Esas cosas suceden.
In Mexico it's also common to commiserate by saying
which means, there's nothing one can do about it. This phrase has a certain tinge of fatalism which is quite common in Mexico. While I can understand why people respond that way, that attitude is not my personal style. You can decide if you want to use it -- but at any rate, you'll now understand the phrase when you hear it. It's quite common, in many contexts.
As mentioned in an answer that the moderators deleted, there's a less polite version of this (which means basically the same thing):
I wouldn't recommend that a foreigner use this phrase, though, as the literal meaning of "pedo" is fart. My guess is that it sprang up as an alternative to "ni modo" because it sort of rhymes and it's sort of a playful variant of the original.
If you want to express the same idea, in an informal way, but without any vulgarity at all, here are two responses you would commonly find in Mexico, at least:
No te preocupes
No hay cuidado
And either of these could be softened by adding "Mano/a" (short for hermano/a, or brother) or "Hombre" (man, but works for either gender). If there's an age difference, then the softener could instead be "Compañero/a" or "Señor/Señora."