i would have to agree the f is the hardest but to me i'm slowly overcoming my fear of key signatures because iim practicing my scales every day for at least 2 hours
Some of the most essential work can be boring, but there is no substitute for it. You don't really know your instrument if the fundamentals of it aren't as natural for you as your eye color. They have to become part of who you are, not just something you do. If you check with any of the horn players you admire so much, they will all tell you the same thing.
I've been playing for over 40 years, and I still do the basics - every day. I still play my way the the Arban's book, cover to cover, over the course of several weeks. I still do basic warm-up drills and conditioning drills and tonguing drills and on and on and on.
There is no replacment for the basics because everything you do is built off of that foundation. Weak foundation, weak building...strong foundation, strong building.
the reson why i practice all of the scales is because i'm auditioning for julliard in 2 years and heard you have to be like, perfect. perfect scales,techniques,posture,and additude