I like to use a Socratic-ish method in my private lessons, and ask my students questions. It means that I have this conversation several times per day:
Me: How did that sound to you?
Student: Not good.
Me: What didn’t you like about it?
Student: It didn’t sound good.
Me: What aspect of it didn’t sound good to you? The tone? the pitch? the phrasing? the articulation?
Student: Um, I guess the articulation?
Me: What didn’t you like about the articulation?
Student: It wasn’t good?
It’s an ongoing battle to get my students to listen more deeply than that. Was the articulation “not good” because it started with air noise instead of tone? Because it was accompanied by an unwanted percussive sound? Was the articulation technique perfect but you failed to follow the composer’s markings? Or was it something else?
Often the “not good” is a combination of factors, but if my students can identify even one of them, then they can immediately start working in a focused way to improve it. If it’s just “not good,” then they tend to just play it again from the beginning without any clear approach to making it sound better, and repeat until frustrated.
Part of my job is to help them identify and verbalize the desirable and undesirable phenomena in their playing, and to teach them the techniques for manipulating the variables involved (breath support, voicing, embouchure, finger technique, and tongue technique, to name the most obvious ones). But it’s up to them to take that information and run with it. For my students to become independently-functional musicians, they need to learn to listen critically to themselves and troubleshoot.
For yourself and for your students, don’t be satisfied with bland value judgments (it sounded “good” or “bad”). Be factual and descriptive about what you hear, and tackle problems in a methodical way. Practice smart!