I need help to understand these paragraphs

Good day, I need help how to understand this paragraph. This is for my report in our English class and I need to write my review about it in essay. This paragraph is from the essay, "Why First Night Seem Like Last Night" by Cornelia Ottis Skinner. I have posted some of its other paragraph before which I could not understand and I had good help from forum users here. Thank you so much for that.

And here is the paragraph that I can't understand(I will underline the sentences that I am mostly confused):

 "    For the nasty thing about stage fright is that its attacks are not limited to opening nights. There are times when, for no good reason, it will strike and there is no anticipating them. You may be appearing in a long run success, assured and cool as a cucumber, when all at once you hear another actor saying his lines and it's as though you were hearing them for the first time and you think, "What do I say when he finishes talking? What the hell is my next speech?" and you may go into a frozen paralysis from which prompter or fellow players rescue you by throwing you a cue, although, mercifully more often habit or the subconscious produces the elusive words, which come forth automatically and often in such hollow tones you have an illusion that a complete stranger is saying them.

This Gehenna of anticipating lines can become epidemic and run through an entire company. Last season, in Major Barbara, it was solacing to find out that a seasoned veteran like Charles Laughton came successfully through an attack; and when, one evening, Eli Wallach went up in a line he knew backward (and was about the way he said it. too), I felt better about the moment when I looked with a wild surmise at GlynisJohns, Who played my daughter and couldn't for the life of me think of her name."

It's the second paragraph that I really don't quite understand. I hope someone would explain it to me. I just included the first paragraph so you would understand the second paragraph. Thank you.