"We all put our pants on one leg at a time"

I am a junior analyst and was recently on a client call with my supervisor who recently returned from a staycation. I quickly filled him in on the details of what the meeting would potentially go over. During the call he encouraged me to speak up and voice my concerns pertaining to any issues with our current processes to the client and to feel free to answer any questions asked of us. So the client asked a question to our team and I completely froze! Yes I froze when the client asked us a question and I couldn't answer. Thankfully my supervisor was attentive and after a few seconds of long awkward silence, he answered the question! After the call my supervisor spoke to me and the one thing he said that I took away with me is "We all put our pants on one leg at a time" he explained that there is no reason to be nervous when speaking to management or a client because they too are people and they may not be aware of our daily processes; hence, the reason they are asking the questions they do. His words really put things into perspective for me because we all are working professionals who essentially want to be ideal representatives for our companies while advancing in our careers. It is very important to be confident in ourselves and what we have learned and speak up so we can move up. Let me know if you have a similar experience or any thoughts and comments.