The hardest part of practicing an instrument (or anything) is undoing bad or counter productive habits. While practicing, full attention to the quality of every motion is essential. I tell my students-
"The body learns quickly, but it unlearns slowly."
Wind players: Are you aware of the quality of your air at all times? Most issues with tone, legato, articulation and attacks are caused by improperly used air and can be solved by awareness and improvement of air quality. I don't use the word support, because most people think and do something tense when they try to "support".
The best advice on air that I've heard recently is from trumpeter Tom Battenberg, a colleague in Columbus Symphony, Ohio. He gave me one tip-
"Don't hold the air between intake and out-blow."
Little does he know, but that is a very Alexander Technique comment. But then again, I'm sure any good idea shares quality with another good way of thinking! I can add to that advice-
"Don't hold or grip your air at anytime while playing."