Testifying of That Which I Don't Know

When I speak or bear my testimony, I sometimes include something along the lines of:

"There are a lot of things I can't say I know or understand very well yet, but I do know (or "but I believe strongly that" or "I have faith that"). . ."

I've found that pretty much everyone understands that sentiment - and only a few people complain if I testify of something I can't say I "know".