It sounds like a general wish for well-being, in line with "Take care" = "See ya later"

I do occasionally encounter folks who take it farther, and they offer to stash my bike in their car and go out of the way to drive me home. I think they see bike riding as a hardship I have to endure. It takes a little work to convince them that I like to bike, even at night, and I'm not just saying no out of politeness.

If they persist, I laughingly tell them about all the money I've put into my safety equipment (headlight, tail light, reflective tape, etc.) and I want to at least get some use out of it.