Student or Learner
I've made worse mistakes in the beginning of my careeer!!!
(by worse, i mean 'more bad")
Any mistake with this sentence? shouldn't it be "AT the beginning...."?
I think that "at" is a bit more natural, but I didn't really react to the "in" so maybe that's okay too.
I think you mean "worse than what is going on now" or "worse than the one you just made, so don't feel bad" right? I wouldn't use "worst." Who knows -- luck may be against you and your worst mistake could still be ahead of you. (Let's hope not!)
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.