Q: When I speak of Kabbalah to other people, I suddenly feel very tired, almost ill. Is this a natural reaction of the body?
A: The giving away of knowledge, especially as opposed to discussing personal feelings, can only do good to people with whom you come in contact. You should not talk of your own emotions and experiences, but you can and should speak of your knowledge. When you express your emotions, others seemingly enter your situation, which might harm you. But you can teach others, and that is completely harmless to you.
You are a very sharp and sensitive person, so during the teaching process you feel the enthusiasm, which is hard for you to let go of afterwards. However, this is a psychological response, not a spiritual one.