1Almost everyone says the same thing afterwards, that the waiting was worse than the thing itself. Say it out loud in your own words, because your own words land differently from anyone else's reassurance.
Before a difficult conversation, write one line about how bad you expect it to be. Afterwards, write one line about how it actually went. Over a few rounds you build a small record of your own predictions running too dark, and that record persuades you far better than being told not to worry.
Islamic evidence
We shall be sure to guide to Our ways those who strive hard for Our cause (Quran 29:69). The striving is met, which is a reason to go in rather than to keep circling the door.
“But We shall be sure to guide to Our ways those who strive hard for Our cause: God is with those who do good”
Qur'an 29:69
Psychological evidence
Work on how exposure practice helps found that neither the drop in fear within a session nor how calm someone felt at the end predicted how well they did later. What mattered was what got learned. So do not judge a hard conversation by how comfortable you felt during it. This comes from anxiety research and is a theoretical review rather than a single trial.
Craske MG, Kircanski K, Zelikowsky M, Mystkowski J, Chowdhury N, Baker A. (2008). Behaviour research and therapy · doi
Review detail
Why it works. Your expectation only updates when you catch it being wrong in your own words.