l'esprit de l'escalier - When you're trying to be smart and the one thing you wanted

When you're trying to be smart and the one thing you wanted to say leaves you and goes to be a smart person.

I told my friend I wanted to be a doctor, and he said, 'Cool,' and I thought of 'At least I don’t have to deal with your drama.'

I told my boss I was going to leave, and he said, 'Fine,' and I realized I should’ve said, 'Fine, I’m leaving now.'

I told my crush I liked him, and he said, 'Cool,' and I thought of 'I’m not cool, I’m just awkward.'