This is a repository for major, life-altering mistakes that you or others have made. Detailed accounts of specific mistakes are welcome, and so are mentions of general classes of mistakes that people often make. If similar repositories already exist (inside or outside of LW), links are greatly appreciated.
The purpose of this repository is to collect information about serious misjudgements and mistakes in order to help people avoid similar mistakes. (I am posting this repository because I'm trying to conduct a premortem on my life and figure out what catastrophic risks may screw me over in the near or far future.)
Not autobiographical, all but one are people I know or have known personally. Which is not to say I have avoided all of these mistakes, but none of this is telling my own story. The ones about reasons for choosing college majors are speculation about other people's motivations, but are obviously mistakes whether they are the true reasons for people's bad choices or not.
Waiting through several years of depression and suicide attempts before telling anyone or getting it treated.
Not living on campus while you attend college, and also not having a car. (Edit: it has been pointed out that this often isn't that big a mistake. These are the circumstances under which I would call this a big mistake).
Not getting good enough grades in high school to get scholarships in college.
Going several thousand dollars into debt to pay for your first year of college classes, and then dropping out.
Living under parents who expect you to do several hours of manual labor per day while attending college, depending on them for rides to and from college, while sinking most of your income and lots of your time into construction of a cabin, far from said college in your hometown, which said parents own the deed to, while you do not have a car.
Registering as an engineering/nat science major in college when you are not good at math or cannot deal with hard work.
Having babies before you have finished all the formal education you want to get.
Not taking the time to apply for good internships during college.
Not taking enough time to apply for colleges during high school.
Not paying attention to deadlines for fellowship and grad school applications in the fall a year before school starts.
Not taking the GREs soon enough before you need to submit scores that you can retake them if you need to.
Not registering far enough in advance as an engineering major to take the Fundamentals of Engineering exam before you graduate (If it's a requirement at your school).
Choosing a major in college based on misconceptions about what you will actually be studying and/or what work that will qualify you for.
Choosing a major in college based on the difficulty during college, and not the effects it will have on the rest of your life.
Choosing a major in college because your friends have chosen the same one.
Choosing a college because your friends have chosen the same one.
Wanting to go into a technical field in college, but not taking the highest math and science classes your high school offers, and being forced to make them up in college (Not very life-altering, but can set you back a year).
My girlfriend was required to live on campus for her freshman year- when she moved out, her rent was $300 cheaper, the apartmant was twice the size, and it also seemed nice to have a freaking sink, and not leave the dog at home. And I would expect the cost of a monthly bus pass to be exceeded by gas alone. So why was this a mistake for you or your friend or whomever? It's not at all obvious to me.