Here I will post my three main shortcomings on the horn, comments and advice welcome!
1. High register
There is a barrier that I haven't been able to break for the past couple of years, and that is hitting B's and C's reliably. Bb's are starting to become easier nowadays, but can still be scary in certain contexts. The high B in the Dvorak 9 solo (and the duet with the 2nd horn) are prime examples of notes that I can't play well. I can't figure out yet how to relax and hit the note, I always feel tense and pinched off, and my tone on that note shows it. Any pointers or strategies?
2. Fast arpeggios
To some players, these types of passages (such as at the end of the Beethoven Sonata) come somewhat naturally. For me they do not.
I am somewhat of a wimp as far as endurance. I never survive long with loud, sustained playing, and often get tired in orchestra, depending on what we're playing (and especially band).