A couple of ways I like to check on pressure in the high register (as in too much!) beside just the sound (the best indicator) is with vibrato, lip trills and shakes, glissandos, doits etc. If you are playing towards the top of your register, you add hand vibrato and nothing happens......too much pressure. Same for lip trills and shakes. If you think you have a killer high F but can't play a shake, you might be using excess pressure (I like air speed instead, through a well developed embouchure!). Think that E is rock solid, but can't doit up from it? Could be the arm strong method is holding you back. Glissando the same indicator. Using efficient mechanics is the solution. The above, along with the sound, might tell you there's a challenge with the pressure you are using. Pushing notes out the back of the neck is another indicator. Endurance, no power, gigs go away, women look at you funny, the rents due.....the pressure mounts!!!