I've noticed if I get out my horn and start playing the highest I can play is a g on top of the staff and it's weak and sucky. After about 10 or 15 minutes of getting my range up there I can play high C's and D's with an ok sound, but still a little weak. I've heard some experienced players say you should be able to get out your horn and play fine, it's all mental. It is definitely not mental for me. I also know everyone is different, but am I doing something wrong? Maybe playing incorrectly the day before or not warming down well?