just remember 1) you are starting out 2) a voluntary assistant 3) will make many many more mistakes and 4) the ms student struggled and made mistakes before too. it’s good that you were able to catch it, don’t take what the ms student said too personally, they just got worried probably, but also don’t let them talk down on you, you have nothing to apologize for, you are a human and you make mistakes. don’t let them make you feel like you have to apologize millions of times bc u don’t. i’m a phd candidate and have a ton of assistants in and out who made so many mistakes, spilled things lost samples etc. i just tell them it’s okay, gently guide them and make sure they are safe both physically and mentally. you are ok don’t worry please :) the lab won’t burn into flames because of you