Before starting a project, a sculptor has an idea of how the project will look, or at least what it is they are sculpting. This is the hard thing with any creative art - having enough direction to get started, but not so much that we limit ourselves. Just as if the sculptor wanted to "sculpt something", we are less productive in the practice room if we just say to ourselves, "now I'm going to practice", or "I will work on my sound". Use your mental image to guide you in your practice.
Once we have the idea in our ear, it is time to get to work. I am not sure if we will ever feel like we have "arrived" at the sound we want, although we should definitely be conscious of if we are headed in the right direction, and of what a "good" and "bad" sound is in relation to our mental image. I know when I sound my best and when I don't, but I never feel that the work is done as far as tone production goes.
This is not to say we will never have AHA! moments when working on our sound. There is good and bad news when we first get a glimpse of our best sound. The good news is we are physically capable of doing it, but the bad news is that now we have to do it all the time (this is not even really bad news, it just means we have to get down to work!).
Anyways, get to work on your sound using your favorite players as guidelines and motivation! Don't be discouraged if you don't immediately see results, and keep in mind that you are likely progressing without even being aware of it. If we see something every day, it is hard to notice changes even if it is changing little by little, as our sound does. Imagine hearing a recording of yourself from a year ago and then one from today. You will no doubt sound better now than you did a year ago (hopefully!).
Keep in mind that unlike the sculptor, if we take a break from working on our craft, it will deteriorate quickly. In this way our trumpet playing is almost like a finely maintained lawn rather than a statue. If you take a break from sculpting rock, it will not grow back and make your job harder the second time, but our sound will become overgrown with weeds and pests if we neglect it!
Thanks for reading, and comment below with some of your recent AHA! moments!