Often, we are nice because we are afraid of hurting people's feelings. As a result, though, we sometimes end up stringing people along and the ultimately make them lose more time and energy than if we had breached their comfort zone early, and communicated our expectations when they weren't yet super-invested. And after all is said and done, if we string them along, they end up blaming us more as well.
This was a hard life lesson to learn, but sometimes, to be kind, one must risk not being nice.
My advice would be: before communicating a tough expectation, do your homework (research how it's done) and be diplomatic. Different cultures have different linguistic paradigms that help grease the wheels towards agreement. Use them. And at the end, be firm but offer support for the transition. If they want it, they will take it. In any case it's likely you will be respected and won't burn bridges that way.