Hello Madridaoi
This is common to lots of people. People just get scared because it is the first few times playing against strangers and you dont know how to react. The best advice I can give you is just to play more and more. Eventually, over time, you will start to not be scared and play like how you play against your friends.
Hi Chess.com , i started to play the game 5 years ago , with some friends , never played before , when i'm playing in real with someone who i feel like he will win , i become the worest chess player ever!!! , i feel scared so much!, no plans come up with my head , and then i lose , even if the other player isn't really good and i can beat him in other time !! , is that some kinda of disease ? it's probably happening to other amateurs like me , so don't be shy if you wanna give me some advice .. Thanks in advance.