Is it proper to say "I forget" when I'm unable to remember something? I've been told I must say "I forgot".
forgot refers to a thing (i.e., past information), whereas forget refers to time (i.e., at the moment):
Max: What's the homework assignment?
Sam: I forget (at the moment).
Pat: I forgot (what the teacher said).
Pat: I forget your name. <It's on the tip of my tongue>
Pat: I forgot your name. <I used to know it>