This is why I so often join my juniors for their training. I think it's really valuable to know how hard something is, first hand. And, I think they respect you more as a coach when you're out there suffering with them, though there is the fine line of making sure they're still the priority.
That fine line is one reason I often do not run everything with them, but I almost always do some part of the training with them and cut short so I can be there at the finish to talk with them, or during intervals, I often run a bit shorter intervals and then see how they are doing; coach or pace them if needed or whatever I can do for them.