I just noticed this morning that I forgot to submit my writing supplement last night, and I submitted it as soon as I could. Is my application considered late now? Did I just screw myself out of admissions?
No, you aren’t screwed. A few days late isn’t going to trash your application, especially since Columbia wants to read your application. It wouldn’t do the school any good to throw away your application just because of a late submission. Don’t worry about it! 
@azwu331 Was kind of concerned about the same thing, because my dad had to pay for the application and I forgot to tell him to also submit the writing supplement with it. I submitted it as soon as I realized, but I was thinking that Ivys are very strict just because of the amount of apps they receive