oder
'Unglücke passieren halt'
oder
'ab und zu geht alles daneben'
usw ...
ovid

Could not resist... I am looking at this poster in my teenager's bedromm everyday ;)

Taoism: Shit happens.
Confucianism: Confucius say, "Shit happens."
Buddhism: If shit happens, it isn't really shit.
Zen Buddhism: Shit is, and is not.
Hinduism: This shit has happened before.
Islam: If shit happens, it is the will of Allah.
Catholicism: If shit happens, you deserve it.
Protestantism: Let shit happen to someone else.
Presbyterian: This shit was bound to happen.
Episcopalian: It's not so bad if shit happens, as long as you serve the right wine with it.
Lutheran: If shit happens, don't talk about it.
Fundamentalism: If shit happens, you will go to hell, unless you are born again.
Judaism: Why does this shit always happen to us?
Calvinism: Shit happens because you don't work.
Quakers: Let us not fight over this shit.
Utopianism: This shit does not stink.
Darwinism: This shit was once food.
Capitalism: That's MY shit.
Communism: It's everybody's shit.
Feminism: Men are shit.
Chauvinism: We may be shit, but you can't live without us...
Nihilism: No shit.

this isn't exactly what you'll write in a report for your CEO...

Jemand hat "Mist gebaut", d.h. etwas falsch gemacht

Noch vulgärer: "Scheisse gebaut"

a (late) alternatve
although it doesn't imply the same degree of negativity as the English.

This is definitely what most germans would say instead of "shit happens" - very common in classrooms :)

is a rough equivalent in Kölsch. In Standard German: es kommt wie es kommt