Ascension is a Pyramid of Effort
This one is pretty self-explanatory. Think of your range as a pyramid of effort. The higher you play, the less effort you put forward. This is not to say that the lower register should be hard work. Quite simply, we're playing a game with our psychological tendency to stress and strain as we play in the upper register. I like to play very slow scales (half notes at quarter equals 60) and as I ascend in range, I continually think about the next note being produced in an easier, more free blowing fashion than the previous one. Work to make it all feel easy. After all, there is a direct relationship between feeling good and playing easy!