I think that now is a good time to reflect on the past couple of years. I've learned so much and I've made some mistakes. I hope that you can either relate to this or come away from it with new knowledge.
Top 5 things I've learned as a freelance musician:
1) Teaching beginners will make you a better musician. I realized recently that between all of my lessons and sectionals, I probably spend 30-60 minutes per day doing breathing exercises, buzzing, long tones, and lip slurs with my students (on top of my normal daily routine). Talk about a fundamental workout!
I think so many people go straight through school to avoid having to teach middle school, and I won't lie, I was afraid to teach this age group at first, too. As young adults, we assume a lot of things about young kids, especially if you're like me and have no younger siblings. All of my assumptions were wrong. Middle schoolers are fun (and funny). And you don't have to baby talk them - you can talk to them like regular human beings. And this may sound a bit harsh, but I'll say it anyways: in my opinion, if you can't teach beginners, you have no business teaching college students.
2) Don't be on time; be early. Get in the habit now of arriving to all rehearsals at least 10-15 minutes early. While you may not get fired from a gig for being late or walking in the door right as tuning starts, you may not get called back to play again. Even if you're still in school, start making this rule for yourself now (I know it's easy to lollygag from the practice rooms).
3) Learn how to double on another instrument. Learning to play bass trombone (decently) was one of the best decisions I've ever made. Not only did I get more gigs, but learning to play with the smaller mouthpiece has effectively made me a better euphonium player too (I've still got loads of work to do, though!). After the last couple of years freelancing, I've developed the opinion that anyone that wants to be a working musician and doesn't play more than one instrument (minus maybe string players and percussionists) is only shooting himself/herself in the foot. Just do it!
4) Bite your lip. I'm still working on this one. I know that saying something negative about someone just feels so tempting sometimes, especially if you're having a moment of insecurity. Don't spend time talking about people (unless it's positive). If someone wants to gossip, find a way out of the conversation. Avoid gossipers all together. They will talk about you, too. On a related note...
5) Don't take yourself so seriously. I went to a regional tuba/euph conference recently, and I was surprised to hear a lot of petty talk during the competitions. You're bad mouthing another group at a tuba-euph quartet competition? Really? At the end of the day, we're just tuba players. We're not working on the cure for cancer. We're having fun. You've got to keep it in perspective - there's an entire world of people out there that have no idea who Arnold Jacobs is, how hard your music is, or what a euphonium is.
As my quintet likes to say... shut up and play! :)