To struggling-for-PhD midi:
1. You 've been working in your (might be tiny) area for such a long
time, and thus you are the one who knows the best about it. Don't be
afraid of the challenges from others, even from the big heads.
2. Don't sniff at the "silly" questions from other researchers around
your work. Most probably it is because you failed to explain them
clearly. Otherwise refer to 1.
3. It takes time to make others clear on your work. But the time pays back.