Final project senior year...
Mistake 1: Chose a project suggested by the prof, who did not initially make it obvious that the project beneficiary would be a personal friend of his.
Mistake 2: Nine of us thought this project looked cool and all signed up for it.
Mistake 3: Looked at the code-behind provided for us and discovered that the web-app we were building was... programmed in Java, using StringBuilder to append HTML, CSS, and JavaScript and create its webpages. Which was then decoded and built into a webpage using some obtusely designed compiler.
Mistake 4: Decided to question the reasonability of said project to the prof.
Mistake 5: Did not quit the project as a group and do something else

We all graduated, I think, but a lot of C-'s were had. Fuck that class.