At the club...

I'm in a club that makes things. At the end of this month, there's a robot competition, a tournament for teams of high school students learning engineering, and we were building a robot for it. Someone who retired as a teacher and now works for the education board sometimes comes to help, but he always ends up messing things up... We had been working on a part for about a month based on his instructions, and we were close to finishing. Even though he was always rushing us, today he suddenly changed the plan... Of course, that part is now ruined, and on top of that, he had the nerve to say, "What a waste of time lol." I can't calm down. I have club activities tomorrow and next week, but I don't feel like going anymore... My friend who worked on the same part feels the same way and is talking about going on strike tomorrow (). What should I do... Sorry for the long post.