Speaking in Public

Two words you have met before

you knowthe new word
حَرِج criticalحَرَج embarrassment
مُؤَثِّر influencerمُؤَثِّر influential; moving

حَرِج describes a situation (الموقف حرج, the situation is critical). حَرَج is the feeling, and it usually sits after a preposition:

Her face turned red with embarrassment.
احمر وجهها من الحرج.

مُؤَثِّر is one word with two uses. As a noun it is a person who influences others; as an adjective it follows a noun and agrees with it, moving for a speech or a story, influential for a person:

The student gave a very moving speech.
ألقت الطالبة خطابا مؤثرا جدا.

The moment on stage

حَالَمَا the moment that, as soon as joins two clauses, like عندما:

As soon as I went up on the stage, I forgot everything.
حالما صعدت إلى المسرح، نسيت كل شيء.

عَلَى اسْتِعْدَاد, literally in readiness, works like an adjective; لِـ names what you are ready for:

I am willing to speak in front of the audience.
أنا على استعداد للتحدث أمام الجمهور.

تَامّ follows its noun and agrees with it: صمت تام, ثقة تامة.

She spoke with utter confidence in front of the audience.
تحدثت بثقة تامة أمام الجمهور.

Advice for anyone

المَرْء is one in a general statement, and it comes with الـ:

One learns from one's mistakes.
يتعلم المرء من أخطائه.

تَمَسَّكَ بِـ is to hold on to something, a hand or a principle, and حَتْمًا marks what is bound to happen:

We must hold on to our principles.
يجب أن نتمسك بمبادئنا.
The audience will inevitably ask you about this topic.
سيسألك الجمهور حتما عن هذا الموضوع.

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