According to Wikipedia, that’s a French term used in English for the predicament of thinking of the perfect reply too late.
For example, you are engaged in a heated debate or argument and you only remember a perfect point of attack after the argument has finished. Or you remember a better answer that you should have given during an examination or an interview after you are out of the door.
Nothing can be as painful as this.
But, should that make us not to engage at all? No.
If you wait to have all your points before you make your voice heard, you might never get to say anything. If you wait to have a full grasp of all the elements of that project, you might never start it at all. The best of our individual truth and knowledge will always exist as an incomplete narrative and we will always need to manage it as such. In this life, you will not know all that you could possibly know at any point in time. It is the truth and we must get comfortable with that. There will always be a loophole in our knowledge bank which makes improvement and development meaningful.
As long as we are mortals, we will grow, we will know better and as we know better, we will do better. That’s the attitude to keep as we engage with life. Make sure you stay sharp and keep learning.