Doppelt hält besser (literally: Twice holds better.) is one of the idioms that you can actually use in daily life without sounding like a wannabe.
It’s something you’d say if you check something again even though you’ve already checked it or if you add a second “layer” of security to something.
One English match is:
Better safe than sorry.
But it’s important to note that the German version really needs something to be done at least twice. So it would be out of place if you check something once, just to be safe.