"Trust arrives walking and departs riding."
Trust takes years to build, seconds to break, and forever to fix.
I've never used this, and, if an appropriate situation arose, I'd probably use "Trust comes on foot, but leaves on horseback." Making Gugg famous.
One related expression I have heard is:
"Trust is gained drop by drop, but lost by the bucketful".
It's a strangely asymmetric process, isn't it? Building trust is incremental, but losing it is binary.