Messed up First System Design Round Ever in 6 YOE

I’m a full stack web developer with 6 plus years exp and I’ve worked in service based company most of my career. I started preparing DSA first as I have never done that being a good developer always in my career never felt the need of doing that. I started with arrays, maps, stack from neetcode and few other questions, I was giving OA in parallel luckily landed an interview for system design. I have never given the system design interview ever and started reading about system design few days back only. I knew I am gonna mess up I have never been so scared or nervous in my life while giving any interview before maybe I wanted that job or a decent product based company so bad that first opportunity I get I messed up badly. I was so scared from the failure that I thought to cancelling the interview so many times but deep inside I knew this is the only way to get into a decent company. I went for it somehow. Interviewer was so friendly also. It was a pretty easy question also I messed it up because of my fear and having no experience in system design interviews. I was not prepared well also for system design interview. I just want to get into a decent company where I can learn things which can help me in my career. I know I’m not a FAANG level guy but I have always been a good developer. How hard it will be for me get into a decent product based company where I can learn things which can make me better at my job? I do not want to ruin my career in a service based company with no learning. I’m following Neet code for DSA and Hello Interview for system design and continuously gonna work on these two things until I went into a decent product based company. Am I on the right track ?? Will I have only 1 or 2 years as my experience is already 6 plus years? As interviewer always expect to go deeper and deeper in system design as per experience. I do not have hands on experience on system design yet. Also can someone suggest where I can give mock interviews to get better in system design? Even if I’m reading any design on helloInterview or anywhere on you tube I understand it properly but after few days I forget things which should be easy to figure out. How should I cope up with this? I’m at my lowest at this time where I have no direction no guidance. I know there are so many good guys out there if someone can advice or guidance would be helpful.